I wouldn't say hurdle - it is certainly doable. It just requires very carefully vetted and tested code. It differs from client/server with additional layer of sync logic between peers.
It also requires making sure that high ping hurts the person lagging, not everybody else. The high ping guy's ship needs to respond sluggishly in a multiplayer instance, rather than jumping around for everybody else. If it's done the other way around, all sorts of exploits are possible (like triggering torrents and other bandwidth hogs when in combat, and just spamming missiles while other people can't hit you).