For a realtime-ish solution I wonder if you've seen Ninjam[1]? It used to be that most evenings one could find various populated rooms; the serverlist[2] shows that the infrastructure's all sat there ready for people to come.

You play over the most recent (eg) 16 bar repeat. At the end of each repeat, everyone gets the updated loop. It's easier to experience than describe but is surprisingly effective and bypasses a whole class of latency issues.

[1] https://www.cockos.com/ninjam/

[2] http://autosong.ninjam.com/server-list.php