[@dragonmancer] I love all these questions! And that is a very good question with how stands will work as some stands are overpowered while some are downright almost useless. I am leaning towards just banning some abilities and having in the application a required clear weakness.

An example of this would be lets say the stands ablity is to be a shield and protect the user automatically, however the stand can only block three threats at a time and the fourth reaches the user. 

Also some banned abilities at the top of my head would be time manipulation, world ending, and unstoppable stands. If someone wishes to let's say have a stand that can wipe things out of existence it must have a very noticeable weakness(such as the target must be touched for 5 minutes before it can be wiped out). 

Stands that evolve are actually very encouraged as hopefully when we progress through the story so does the character and stands however it must be noted that the stands potential to evolve is high as to avoid cheap ways out of a situation by magically evolving with its potential at D. Due to Hamon users being rare at this point (with few masters left of the art) anybody wanting to use this needs a very good explanation of how they learned the art. People wanting to use a stand with Hamon abilities should only have the basic knowledge so everything is fair.

As for the RP it might be tomorrow as I have been working on it for awhile and now stuck on how to words some things such as limits to ablitites so new players to the series are not terribly confused.