I can't give you rigth away a list of "this won't work, that will work".
BUT, I am sure I can get a lot of that info for you in a matter of days.
And, if you are interested in giving this a try, I can maybe provide you with a deblobed kernel. Even more, I can try calling in some other people (who know how to handle this stuff way better than me) to help!
I think I would pose things differently: what do we have to gain by using 100% FLOSS?
Well, from a security point of view, there are no closed-source / binary-only programs running, so if a bug or exploit arises, we can handle that ourselves. We don't have to rely on any other party to solve the issue. Think about Adobe Flash, for example. A security nightmare that only Adobe can solve. And they never did so. Good thing it's almost gone :-P
From a privacy point of view (for me it's very important), we are sure what the machine is doing. No chances of a backdoor or unknown bug that activates microphone or webcam without telling me first. We can be sure that no driver or firmware is sending any sensitive information when "doing an update", or "filling a bug form".
From a hacking point of view, it's much more liberating, powerful and even FUN! Not having to deal with closed source binaries we can see everything that is happening in the system, and we can change everything. We are totally free to deal with things our way.
So, you see, maybe some things will need some additional work, but I believe we have more to gain than to lose.