I think we should first define precisely what is tanking before talking about how to penalize them. My take on it:
1. Tanking a match. You can field 5 players and still tank a match. You just need 5 2k-salary-players. But if you lost 30 pts for TIE vs TIE, 50 for TIE vs normal, 70 for TIE vs CT, that's tanking a match in my book.
2. Tanking vs Build-up strategy. BB actually acknowledge some build-up strategies where you somehow sacrifice something now for the future. From what I see in the game design, their response to our questions...BB would tolerate it if we only tank a bit. So we should draw a line: if you are still in the cup, you play 3 matches a week, it's reasonable to 'tank a match' (see above) out of the 3. It's only tanking if you tank 2 of them. If you are out of the cup, you play twice a week, 'tank a match' out of the 2 is already tanking.
Basicaly it is defined nicely.
I will add that it is not exactly true.
For a team who is promoted the differences are huge, and those cases can happen even if they will do their best.
What can be examined are the following:
1) What is the extra free money a team has in the bank, comparing to the value of his best player.
This value may be due to a very recent selling, and hence needs to be ignored for a short period of time.
2) Which players where chosen to start a game, in terms of value. Choosing none (or just one) of your best-five is suspicious... Of course, injured players are to be taken in consideration when doing this examination.
BTW - one of the reason that tanking is so widely used in this game, in opposed to the NBA where tanking start very late in the season (if at all), is that this game as serious competitiveness issues, as I've provn more than once.
The only thing that bother me is that the they decided that the most urgent thing to do was to add that additional statistics and not resolving the real issues in this games.
Hence, I'm not sure what good this forum does.