Feature or MOD about a new voice into the post form

[lucablue]

Hi,
I've bought the CMS few time ago and I'm still learning how to use it to the best for my objective.

One feature I need is the possibility for my users to write post by post the name of "character" who is speaking in that moment.

I'm trying to create an Role Play Game board and I'd like to have the possibility that in each forum will compare:

USER's Name (as normal) and on side his character name he would make speaking.
Moreover if a reader want to speak with this character (and no to the user or author) the Private Message go to the USER mailbox but with subject the name of character instead the name of the thread.

At the least also the picture, avatar, is changable every time the user post, to put the image of the character and not his image. (and is only for that post).

Is possible all of this with a MOD you know and can suggest me or create it to make optionable?