After reading an article called "Create games not game engines" or something like that, I thought indeed the best idea for this game would possibly be to start from scratch. At least for my benefit it would do a great deal in teaching me the programming concepts of developing a game, so I've started with XNA and C#. Even if I only create a 2d prototype of the final version of this game, I think it will be a great learning experience and a great way to find team members along the way. I really appreciate everyone's input so far and will likely need very much help throughout the process, so I want to keep this thread going.
So CPU freak, you think it would be pretty feasible to implement that map editor into the gameplay, so that a player could maybe select from pre defined walls, put them together on a grid, and make a house. Or maybe the player could just select from static models and place them down.
And yes I'm looking for a FPS MMO, but the building and the MMO would NOT be taking place at the same time. The MMO world would be static and persistent, but at any time a player could say >go back to my house, and be in a little personal loaded level saved on his computer that he could edit. then go back to the MMO world, find a friend, and connect P2P and the map be loaded upon connection. Probably will want to delete it after from the visitors computer after the seesion because it will be different next time.
I am only attempting a 2d in order to start producing some content and find team members. If things look more promising in the direction of that engine (or if i find a programmer interested in taking any other direction) I will be more than happy to go that way. But I do see nothing wrong with a potential MMO with personal building instances working out in the C# and XNA environment, and with C++ implemented if needed. And I'm not sure about porting to cryengine, so maybe or this could be a prototype to gain a liscence. or maybe we could develop the next engine to rival theirs
or maybe it will just be a very fun 2d or 3d open source game.
I appreciate all the help lets keep talking the possibilities and if anyone is interested in seeing a game like this succeed let me know, I can provide more information.