It should be pretty easy if you find a bootloader that will support booting the different images. Else it should just work. But I don’t know much about phones. Based on the SD801 a few half-free OSs could run on the FP2, I made a list here:
Else I agree with @apheiner. Nice to have for the pro user, but most users want the fair feeling and support the campaigning, but in the end they also want their app stores and the fast “candy”.
In the end it all boils down to the support (can the FP project handle at least one longterm stable OS?) and the consumer wishes the users have already grown used to (I want my app now! Everybody has it!).