You might want to use a system like Symbaroum, which is streamlined in comparison to D&D. You can pretty easily adapt it to the setting if you need.
Alternatively, if you'd like to use Hammercalled (the game we're working on), I'd be happy to work on making it fit a PBP format for you.
Sounds great. I would love to use Hammercalled.
Any chance you could help send some players my way ?
Or any type word of mouth would be awesome.
Thanks for reaching out
Sadly, I have no players to send (none who use steem, at least).
However, you can get all the stuff for Hammercalled here: https://www.dropbox.com/s/c0kpbz246y2thkf/Hammercalled%20Rules%20Reference.pdf?dl=0
It's something of a different animal than D&D in some ways, but it is built to run fast (combat should take 1-3 rounds, unless people decide to string it out, one roll for pretty much everything outside combat).