There is a fine line between cheating & twisting rules to take advantage.
Without going to personals, let me put my thoughts on what actually is ball tempering. To me, ball tempering is an act to deform the ball with substances carried outside of game or person. Let me explain -
The mechanics behind swing of cricket ball is known to everyone - but, I give a very raw explanation. A cricket ball moving in air at 125K+ speed receives lots of air resistance; while the seem at ideal position works as a keel in motion. Common knowledge is that you keep the ball shining, air resistance will be low and keep upright seem with a slight angle (in wards or out wards) - you get in or out swing - conventional swing. Now, some players found it out that, same mechanics but you keep one side roughed up and one side polished, that conventional swing behaves irrationally - add seem position, wrist work, thumb, middle finger ..... you can do miracles with old ball, more than the new one with is hard and smooth in both sides.
Now, to achieve that players give lots of efforts - some legal, some illegal and some in between. For me, at the strict most judgement - every act on ball is illegal. One shouldn't shine it on the groin, because that changes ball condition from natural course. One shouldn't use sweat or spit on the ball to make one side heavy, one shouldn't touch the seem and one shouldn't drop/bump the ball.
But, there are acceptable acts which has been practices for long, like the ball shining, ball wetting (with sweat or spit), ball drying by the use of a towel or with darts from ground.
There are in between acts - which might not be in the perfect spirit of the game, but you can get away with, may be twisting fair play. One such act most teams with spinners do - that's bumping the ball on one bounce - it's not illegal, if fact as kid, when I was learning the game (not in BD), my coach used to tell us that close-in fielders MUST send the ball to non-striker end at one bounce (but not half-volley); because that's the fastest way to reach the bowler without crashing his palm. But, teams over do this often - unfair, indeed; illegal - no. Also, in olden days, there were many grounds with concrete outer ring - players deliberately allowed ball to roll after boundary and hit the wall .....
Then comes plucking the leather or seem with finger nails - human nails are not razors, you can't slice seasoned & burnished cow hide with nail, neither can pluck high grade fiber used to sew the Test grade ball. What players did (still do, but now keeping umpire in loop) is use finger nails to remove small pieces from ball, shape the seem ...and to the extent of plucking out the seem so that umpire changes the ball. Worst I have seen a player biting a ball, but with his own teeth - at least he didn't bring extra set of teeth and he can't unlock his jaws to keep teeth back at home
3rd level is using substances that a player carries with his person as a dress code (not born with it) - zip is the obvious example, and then there is examples of bowlers deliberately stepping on the ball while fielding and use spikes to create dent on the leather. But, in past I have seen many such acts and quite innovative one as well. I have seen players coming with heavy hair gel and then rubbing the ball on head. I have seen bowlers using that zinc layer (not sure what it is, Umar Akmal uses the green colored one) on ball. One classic story (example) B$ Bedi told, that in 1976 Delhi Test Peter Lever ran through Indian line-up with a "heavy" ball. At the end of the Test one of the Indian players went to Lever and told him point blank - "stop this kidding, we knew better use of Vaseline from our teen days

". Worst I have seen is players carrying key ring while playing (absolutely no reason to bring keys when you are playing Internationals).
Next level is using/bringing substances from outside the game, that doesn't belong to the body or the game - one classic example was Mike Athers, a perfect gentleman who must have done that from naivety (I actuality do trust him). I have seen players plucking metal pieces/bottle caps from ground and "act" on the ball; I have seen players using wicket (stump) as a spear on the ball ...
Finally, we come to a deliberate, pre-planned act of cheating, when you accomplish the task collectively, and you bring "customized gears" for that - a gear that you can't explain why should it be in a cricket field (even key ring has a story - recently I caught my wife stealing money .........).
To me, 1st one is absolutely legal - you have to give bowling side some space.
2nd one is against the spirit of the game, but not punishable crime at first go - umpire is enough to handle the issue - call the Captain, ask him (his team) to behave for 1st offense. Then 5 runs penalty and I don't think it'll go to 3rd level thereafter.
3rd & 4th one are 1st & 2nd degree of cheating, but again it's often personal choice and a soft cheating, which most cases is a temporary act - that, player (s) is trying to gain some advantage for a specific period. A strong Match Referee is enough for this - penalty, fine, ban .... it should end there.
The 5th one is a serious offense - it's a crime in cricket context. You are nurturing cheating to the level of proficiency and sponsoring it from Management level. It shouldn't end only at Match Referees' office.
Aussies are getting too little, trust me - too little for the act. This is faaaaar beyond Tony Crafter umpiring at home Test or Shane Warne taking payment as a weather reporter. Now IPL is there for BCCI, so you might not feel the heat - turn back clock 20 years back - on same act, trust me IND-PAK cricket would have been mutilated, trust me literally shredded into pieces, and SRL, BD would have been used as a scarecrow ...... Aussies were not even fined 5 runs!!!!!!!!