Hmmm...
I'm actually all for you getting back into writing Ranma fanfiction... several existing stories come to mind as desireous of being continued.
As for DXD... If post Ranma manga, that group likely would be doomed, at least if they acted as they did in canon... if during, it would likely depend when...
But even if not... where would they stay, and why? What would draw them there? Someone with a sacred gear? Who? To be quite frank though, I think Nerima too chaotic even for them to survive...
Also, the drawback of using Nerima is you lose out on all the possible interaction that could occur were they at Kuoh Academy instead because you got the devils territory there..