From 1876, only for like 5/6 years... Australia was not among top 2 cricket nations in world - of those 5/6, half was due to the self exiles of top 10-12 cricketers (for Packer cricket), and another one was due to rebel tour of South Africa. Point is, it's almost impossible to select top 11/12 cricketers for Australia - every generation, they had an XII with contemporary top cricketers.
Still, here are my 12 (with 12th man) - more than stats, players are chosen for their dominance/reputation during contppemporary era
1. Vic Trumper - yes, someone with a Test average just under 40. But, Vic Trumer was like what Viv Richards of 1970s during the first golden era of cricket (1900-1914). Brilliant stroke maker, a tough nut to crack and a tremendous fighter - many of his runs came when chips were down and like Viv, he used to target top opponent bowlers. Won't go to his technical ability understandably (as Jack Hobbs was the standard for batting technique of that era & I have seen some footage), but guy averaged around 40 in an era when 35+ was rare for anyone playing more than 10 Tests.
2. Hayden - we have seen him. What makes him stand out against other possible candidates (Taylor, RB Simpson, Lawry, Morris, Woodfull, Ponsford, Warner, Slatter) is his spin playing capacity for an Aussie. Besides, it's a nice left-right opening combo.
3. DG Bradman - Average 99.94 for 6,996 runs ....

4. GS Chappell - Greg is often under-rated as a batsman because his career cut path with someone Viv Richards, besides he was reluctant to travel outside (never toured India, WI, only once), and often used to take off (hence ended up playing only 87 Tests in 15+ years). But, main reason is - we never recognized the best of Greg Chappell. Between 1977-79, he played about 20-25 Packer Tests against most of the best bowlers of the world and scored over 2K runs at 65+ average - may not be officially qualified, but for me those runs were more valuable than most of the Test runs in that era. An equally brilliant spin player (Ask PAK spinners of that era) and among the ATG slip fielders - he'll always be my No. 4 for Baggy Greens.
5. Allen Border - this one was the toughest, because this is the last specialist batting position and I had at least 6 others to consider - Neil Harvey, S Smith, R Ponting, Stan McCabe, S Waugh, Clem Hill. I went for the lefti and the only Aussie batsman who had to fight against the odd - for that his career encompassed those 5/6 years I mentioned and he averaged like 60 in that era, fighting almost alone. Besides, he adds a special feature in Australian cricket - a Slow left-arm orthodox spinner, hardly any found there.
6. Keith Miller - the greatest fast bowling all-rounder ever, before someone Imran Khan came. Probably the best ever Captain that Australia never got (because of his differences with some DG Bradman, a great but mean character, who always had something against KR Miller, apparently because Miller was more popular among team mates!!!!). Miller was good enough to make any contemporary Test team simply as batsman .... and then guy averaged below 23 for his fast medium bowling.
7. Gilchrist - not the best WK (I believe Hilley, Marsh, Tallon, Grout were better gloveman), but the impact that he created batting from No. 7, actually had changed the landscape of cricket. I always say, that frightening Aussies were almost unbeatable, not because of Warne, McGrath or Ponting, rather because of this guy. He was a master of batting with tail and he scored quick - countless time he had taken Aussies from a 50/50 position of say 203/5 to match winning 353, in no time - those extra 75-100 runs for last 5 wickets were killer against that team.
8. R Benaud - yes, I'll play two leggis. With Miller in the team, 4 pacers is a bit luxury unless the wicket is one-sided (Apart from WACA, every other AUS tracks, I'll always play two spinners). Apart from being a brilliant, brilliant leg-spinner, Benaud was quite a decent bat, his stats won't justify that, because guy didn't enjoy batting. He was more focused on bowling and how to get wicket (even when he wasn't captain), but no one in history counted his runs more than this guy - I had checked scored cards of his entire career of 63 Tests, that guys was made for scoring invaluable runs from No. 8/9. He retired at his prime, because he was too proud not to make the team as Captain first (though, he was only 33 when the played last Test - could have been among contenders of MoS in his last Series). And yes, he'll be my Captain - undoubtedly the greatest cricket mind that I have ever read or heard from. What little I know about cricket, lots of credit goes to this guy for his time in Channel 9, ABC commentary box and his books.
9. Warne - simply because he was Shane Warne
10. DK Lillee - may not be the greatest fast bowler that I have seen live or archived, but no one was more complete that great DK. The mentality, the fighting spirit, the commitment that he brought to the team is unparalleled - probably the toughest opponent on the cricket field along with Imran. Like Greg, his best two years were lost for WSC, where he took close to 100 wickets at around 23. His career stats were tarnished for one horror series in Pakistan, but you don't dream of a better man than DK Lille to lead your attack.
11. McGrath - The perfect, all wicket bowler - the greatest metronome. If anyone ever can be ATG in cricket filed without looking that impressive or spectacular, it has to be pigeon. I still wonder how this guy took so many wickets, bowling like a bowling machine, but I am sure the top batsmen of his era can say better. He indeed was monotonous, but I haven't seen anyone doing a repetitive task so perfectly.
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12th man - this one is the toughest job - I have to choose one from about 20 cricketers (all of whom are great to ATG) to carry drinks!!!! I'll take out batsmen from this list because with Miller, Gilchrist, Benaud & Warne from 6 to 9, I'll never play 6 batsmen for Aussie XI.
I can go for all-rounders - people probably don't know much about George Giffen, Monty Noble or Jack Gregory, but they were Kallis, Kapil, Imran of their era - trust me. Then comes Davidson, for a short period Gilmore as well (before wasting himself to booze), but this team doesn't need any all-rounder - two of the greatest are already there and Warne was a border line bowling all-rounder.
I can go for a back-up spinner - Grimmet, Tiger O'reilley, Ranji Horden, McGill, Ironmonger, Miley, Trumble, Vic Saunders or Lyon... but I have already 2 in XI + Border has a Test 10 for.............
So, it has to be a fast bowler. I have about a dozen to consider from 140+ years of glorious history - from "Demon" Spofforth, Charles "Terror" Turner to Pat Cummins, Josh Hazzlewood and in between Thompson, M Johnson, Alderman, Lee, Gillespee, Mackenzie, CJ Mcdermott .... and I am sure I have missed few.
But, the two fast bowlers that really is contesting for this last spot are the current Captain - Cummins. At 18 years of age that kid debuted in SAF and I was impressed.... not for his bowling (Though he did take a 6 for), rather for his fighting spirit and boldness with bat - chasing 310, he came at 292/8 with Styen & Phillander just removed 2 batsmen with a 2/3 overs old 2nd ball, kid back drove Styen for 1st (or 2nd) ball, and then took a single of the last ball to face Phillander!!!!... did end up hitting the winning shot. I knew, that kid will lead Australia one day - though they hardly ever made fast bowlers Captain - not even DK or Mac
The other one was Raymond Russell Lindwall - to most Aussies, before some DK Lillee came on to seen, this guy was the greatest fast bowler for them .... and then guy has two Test hundreds!!!!
I'm divided between the two, but I'll go for Cummins, just because we need a representative from 21st Century. And, he'll be my Deputy - simple reason is, if I play 4 pacers, Benaud is the guy to be dropped for Cummins. And, that team has 5 other great, great Captains - Trumper, Bradman, Greg, Border & even Gilly .... I just don't want any of them to be deputy.
So, my team has 1 from pre WW I era, 1 from in between 2 WW era, 2 from 50s-60s, 3 from 70-80s, 4 from 90s-10s & 1 from 2010 or later.
To be honest, I don't like Aussie cricketers, hate might be a very harsh word, rather disgust is probably more appropriate for that they'll keep you honest in a cricket field till last drop of blood - but that doesn't stop me respecting the greatest cricket nation in world - they have produced the most number of wonderful cricketers that you might not love but must admire.