I'm not sure what you mean by build off of but there really isn't anything you can do to an AR180B other than add a crappy quadrail and an AR stock if your willing to hack up your lower receiver.
I'm hoping CA's 180 project will change that. If I'm lucky enough to beta test the lower and then if they do an upper and I end up being a tester for that which would give me a free complete rifle I'm pretty sure I'd still buy another complete production rifle. Don't worry, I'd wait to order one for a while so guys without one could have one before I have three. I'm a nice guy like that, lol.
My 180B is about to get an ALG ACT nickel boron trigger, it's in the toolbox just waiting for me to get motivated. I have one of these triggers in an AR and love it, it's a nice single stage.