First of all, one question.... is this an official topeleven forum or they are chats between friends?

Here are my suggestion to reduce tankers and manipulators and increase the fun and the effort to keep a team at the top:
1) apply the 20% reduction at the end of the season always, not only to promoted teams
2) if the draw depends on the mean strength, calculate the mean considering only top 11 players of the team and during all the season (for each official game)
3) if the draw depends on the mean strength, reduce the range from the hypothetical current 20% to 5%
4) in auctions now you can buy only 99% players from the start to the end of the season and this favors the mechanism of sell and buy players. The % of the players you can but should be progressive: 99% at the beginning of the season, 110% in the middle and 120% at the end
5) even maintaining the current draw system, introduce and expose a world rank chart. This rank should consider the mean level of the league where your team was admitted and each point got during the season. Ideally if you are in last position of a [100-120] league your rank should always be higher than the rank of a team in a [90-100] league. The rank should also consider the history.. if your team was always promoted and if not, your reputation should be penalized (tankers would be penalized).