I read that.

Respect for being so helpful and active member of this community.

Your suggestions in short:
Remove the option to play again in CL if won the CL/SL of previous season.
Also if the treble is the ultimate target and a tanking team isn’t playing for the CL/SL, must not participate in the Cup too.
Max quality of a player could be 8*, 140%. If someone wants to increase the quality more, could do that only with buying tokens and use the personal trainer (not with saved tokens).
Rewarding is always better than punishment.

Not letting CL or SL winner play next CL is not right way in my opinion (who needs my opinion anyway )

Imagine that you won CL, but opponents in your league were very strong or there were crazy results, like in last season, when lower quality teams were constantly beating stronger teams in league, and you finished lower than fourth place.

And I totally forgot about Cup! You won Cup - you promoted!

That's what they do. They win everything, but league. That's why they stay in same level.

Give them reward!

Winning CL, SL, Cup or any of the events gives you promotion to next level.
Your Asso promoted - your team promoted also!