I like your idea of the character show off, I've always been a fan of showing off my character for various purposes. I gave a similar suggestion but in a more simple form(eg: when you check someone, or look at your gear via the menu) I think the only issue with the 3d model would be how many resources could be spent.

Also that would be very nice feature to have a list of retainers, but since we have all these XIV communities available wouldn't that defeat the purpose for them or do you think they could co-exist with each other?

and an App would always be a good idea