only division III teams whose world ranking is never higher than the median world ranking of all division IV teams can follow the world ranking fully, instead of the current method.
If i understan correctly, only newer teams this way could be paired with lower division teams in bbm tiers, and not deliberate tankers playing for years and years, right? This could be nice change and extended to all leagues not just III and IV. Of course that way you couldn't get 1024 teams in most tiers.
I personally wish there was no overlap of different division teams, except like you mention newer teams. Tier 1 for I division, tier 2,3 (4?) for II division and so on..
I know a team from my nation that tanked its ranking and got into bbm tier 2 while playing in Heaven (one of the strongest top leagues). Needless to say it dominated that bbm tier, where almost every team is from division II and it's only real opponent was another top league team that somehow got in.