In some lower leagues you could win even while being below the salary floor. Obviously there should be different constants for different league levels. Should they tie it to the whole season running salary average or start of the season salary etc. There are a bunch of things to think about.
I shouldn't be punished for training salary efficient players.
This is a really strong statement. Should a team be punished to spend anything if he can outplay 4 bot teams in his conference? Perhaps that one more salary efficiant player "you are punished" to add, might take you to promotion level (while your opponents are already spending over the raised floor)? Maybe your leaguemates are not good enough or are more focused on cup games. Maybe your memory fails you (we can't actually check if you are telling the truth here, or remember the facts correctly, right?).
We actually have no real parameters for tanking teams. I just hear: "everyone is doing it", "it's the only tactic available if you want to win" bla bla bla. Then there are the suggestions how to spot and punish a tanker. If a team loses by (insert any number here). If he loses (insert that number again) 2-6 (whichever you like of these numbers) times in a row. Has walkovers in a row. Has (insert number again) walkovers in a season. All this is irrelevant tbh, as teams have different league/cup/tvgame/rivalgame you name it goals. It's called tactics to get ahead of your league-/countrymates. If it sometimes requires you to start your subs and have towelboys back them up, so be it (unless ofcourse you want to train GS the whole season).
Obviously we still need to leave some leverage in the salary floor (for teams who have been sitting in +-0 for a long time and have a team full of 33+ players), to actually make some money and help teams get back to their feet. But the current salary floor in the top divisions is too low.
With salary floor we are not trying to punish salary efficient teams, but trying to limit excess income for teams who are not trying to compete.
NB! I think your idea of tieing fan reactions to available funds is a good one. But I think most of us know that "The general manager is doing everything he can to try to improve the team" and "I am familiar with the star players, and am not afraid that they will be transferred" are not really heavy hitters compared to "The team played well in our last league game" :)...