Method 1: Training Stats after ranking up.
This method is like when we rank up from D-C or like C-B. When we rank up we get a certain number of stat points to distribute into out stats. This method involves that. Once a member hits C-rank they get 10 points to put into a Stat or stats. I suggest that once they rank up they get instant stat points and trainable stat points. So once someone get to C-rank they get 10 points to put where they want. They then can have like 10-15 or a different number of trainable stat points they can earn later. Once they reach the number they are capped out on training stat points.
Ex. James just hit C-rank and has put hit 10 points into Str giving him 11 Str. He then trains 10 more stat points and puts then in End, giving him 11 Str and 11 End.
Method 2. Training Stats monthly.
This method would allow members to train a certain number of stats per month. It can depend on rank or just be a flat number. Take 10 points. Train all 10 and you must wait until next month.
Ex. John is B-rank and hit Str is 20. He trains his 10 points into Str and is at 30. John knows he has to wait now until next month to train atleast 1 more point into Str to deal B-rank damage with hit hits
These are just 2 methods I thought of, let me know what you think.