Now that I'm forcing myself to come up with stuff I'm finding it's not all that much worse than what I would normally come up with, and it's actually inspiring me to come up with song ideas that I would have never made if I hadn't taken on this challenge (most notably song #6 which I finished yesterday is a bizarre long dirge-like ballad with no repeated melodies that incorporates spoken-word sections and ambient noise. I don't know if it's good but it's certainly not like anything I've ever done before). There will undoubtedly be some duds by approaching things this way, but I think that's part of what makes it interesting.
The biggest challenge I've found is less the coming up with song ideas and more the actual recording and production. I've gotten a lot of practice at mixing over the past few years, so I'm pretty good at getting good results fast as far as that aspect is concerned. but I've always tried to rely on other musicians for the instruments I suck at (which is anything other than rhythm guitar and drums) and it takes me a lot of takes to get a vocal performance I'm OK with. so that adds a lot of difficulty to it.