great idea

that said I don't think you can customize DID systems. its one of these situations where each persons system is exactly the way it should be in order to survive. for some reason while you were going through all the trauma's that you went through you ended up with what you have, that helped you to survive, grow up to be who and what you all are now.

that said some peoples systems are the kind that my location calls evolving, where there are alters in the system who's sense of agency is to continue to learn and grow.

since you seem to have a great deal of co consciousness with each of your alters maybe you can find out if your system has these kinds of alters that can help everyone to get along better and get their needs and wants taken care of.

maybe you can pick a day where it doesnt matter whether you wear nail polish or not. by the way here in america even normal non mental disordered guys wear nail polish, color their hair, even skirts/ dresses with out any retribution from things like getting beat up, bullied or made fun of. here in america we have this equality movement things going on where being different is perfectly acceptable now, we have the metoo and others too.

we even have adults copying their facorite music and tv/ movie stars when it comes to dress codes and make up and nail polish....

my point.... i know someone who was afraid to let their opposite gender alters be what ever their sense of agency was but then decided to try something different and told their friends hey I saw this music video and decided to try this nail polish on for size what do you think... now his friends fully expect him to show up in dresses, skirts, picks, purples, make up, nail polish you name it.

another one of my points in todays world there is a way that will allow things for this to happen without fear of aggression. maybe you can start out with a bit of cos - play.... copying your favorite actors and actresses / music artists. then work your way into letting your alters be who and what they are.

just a few suggestions