Can this be setup on web-hosting rented from somewhere and just pointed at CGMiner via API?
Yes, but you need to open cgminer RPC to the IP of that server. That is actually exactly how I had it set up before on coin.mrbrdo.net (still works but old version).
This looks awesome! Any chance of adding per-rig management of pools? I'd like to be able to add/remove/switch pools on a per rig basis, ideally with a way to group rigs together and make changes on a group at a time.
This is already implemented, you can add a pool to all rigs, and switch pools per-rig. I will add more features for this later probably.
Does this need to be run on a miner, or can it be installed on any linux machine on the same network as the miners?
It doesn't need to run on miner, it can run in local LAN or even on remote server if you open ports and set api-allow correctly.
I've started with 700MB available and it still ran out of space.
can u check if anything went wrong?
At the end it shows that you have no space left.. So it seems you need even more space. Weird, but it seems so.
It is a bit weird because I was able to install on BAMT without resizing partition initially. But perhaps there are temporary files it needs while building and you run out of space while installing. Try running
rvm cleanup all
bundle install
script/puma start