Regarding hacking 5E to better suit my tastes, I want to make classes a bit less fiddly, but mostly I want social and exploration to have the same level of support as combat. I think I can build social encounter and exploration challenge systems that essentially work just like combat.
Level Up does a lot in that area, but I feel like it can all be even more thoroughly integrated. I have the LU pdfs, but now I'm tempted to get the print versions as well.
I'll be keeping a keen eye on the Black Flag project, too, and other 5E-compatible innovations.