I suggest any Bijuu, main ability rule or Specialty changes be proposed to me first. I worked on those heavily to balance them within the game and allowing higher/stronger power combinations with those will only hurt. Numbers will need to be retweaked, entire abilities altered or removed and the pathway layout itself changes with the more abilities a Bijuu can have in addition to the Pathway itself. The more it has access to, the weaker the core skill will become as a tradeoff.
I dont want to discourage creativity or change within the rules, but rule changes arent always as simple as "well i dont like this, lets update it" or "this feels like it should be allowed". A lot of aspects of the game must come into account when designing changes, especially all the ways things can (and often wi) go wrong from a change.