I will try to promote my idea against tankers harder (hopefully I won't get punished for it).
Mostly tankers use their advantage to win Cups and Champions League.
Solution is here. Need to make new simple rule - Winning Cup or Champions League gives team promotion, no matter which place they finished in their League.

There is still reason to tanking to get better over seasons, but tankers won't be able to constantly use their positions to win Trophies over and over.

Now in my League in level 7 is a team with 26 Cup trophies.