Thank you Kukoc for these well-thought out and well-put suggestions.
I like 1. It could include staff salaries too. It makes sense to have to balance revenues and expenses.
The penalty could be lower as I think the possibility to overspend for a while should still remain.
I don't think 2 and generally salary floors are necessary or efficient.
Hit the wallet ! Teams who field blatantly understrength lineups should be severely hit on their income, arena receipts and merch. It's conceivable to cut TV rights too, it would need more thinking and analysis on the consequences, so I'd be careful touching it.
This in conjunction with 1 would lower the team average total income for the next seasons and would be enough to negate the point of tanking.
I don't like 3. Most transfers are legit, why hurt everyone ? And would it work ? I can see ways around it and I am not the wicked kind. Both problems you want to fight with this are minor in my eyes and the solution is too drastic and with fallouts on the market difficult to predict.
Suggestion 4 is not necessary with your 1 and my 2.