Personally 3 things for me
1st: Removing the restriction that all dark release techniques above B rank require Inhaling maw, it wasnt a rule then it and personally i think it shouldn't be, it restricts the KG so much to the point where everyone just meta games and doesnt use any elements we can absorb so it makes our KG practically useless when the opponent is just spamming earth and water cause their bio auto knows that its a dark release user. I also think it'd create alot more fun instead of having to wait around, absorb a jutsu and then use it
2nd: Create the Jashin clan. I love Hidan as a bio he is amazing but he just doesnt fit my personality, the battle style is spot on but i find it to hard to RP as him as it makes me feel like a douche. I also think it'd be nice to explore Jashinism more inside the RP and it oculd become something fun(ofc it'd then need ot be restricted or something, perhaps no KG or HA, have it like a KG rules or something)
3rd: Remove the sensei only restriction on MS, if someone is good enough to weild 3t sharingan and pass the test they should be allowed to without having to become a sensei. Not everyone wants to teach some just want to RP, but how can one RP with a bio they can no longer progress with without being something they dont want to? Of coarse i'd say this person(like EIG) would need the approval of perhaps 2-3 MS weilders(only ones i know are LoK Lili and Ryujin) to take the test. I think it should be available for everyone as long as they are proficient enough to weild the MS why not let them, its a bit unfair to force someone to become a sensei if they want a complete itachi bio or shusui bio ect ect.
Apart from that i cant think of much else on a personal note