Respectfully disagree. I found Promethea to be poorly executed. There was a decent idea somewhere in there, but I think he was too distracted by the magic system to find it.
One exception -- the aside about how the Christian and Muslim Prometheas fought during the Crusades. That was nicely done.
Yeah, the plot suffers bits falling off the end. Not the sides, thankfully. I think it's at least as coherent as Miracleman, and nevertheless remains an excellent exposition of alchemy and art.
I've often had half-finished LW post ideas and crossed them off for a number of reasons, mostly they were too rough or undeveloped and I didn't feel expert enough. Other people might worry their post would be judged harshly, or feel overwhelmed, or worried about topicality, or they just want some community input before adding it.
So: this is a special sort of open thread. Please post your unfinished ideas and sketches for LW posts here as comments, if you would like constructive critique, assistance and checking from people with more expertise, etc. Just pile them in without worrying too much. Ideas can be as short as a single sentence or as long as a finished post. Both subject and presentation are on topic in replies. Bad ideas should be mined for whatever good can be found in them. Good ideas should be poked with challenges to make them stronger. No being nasty!