Don't you just need to setup a VPN and have everyone connect to it? Latency may of course become a problem if the game expects it to be near-zero, but if it originally played fine over the internet then maybe it will be fine with some.
Never tried myself.
Trying to find 8+ people that you already know or that you might want to play Far Cry multiplayer with, who also are capable, willing and able to install and set up one of the popular VPNs used with gaming, and walk them through optimizing the configuration to work as best as possible through their firewalls is a huge pain in the ass to do with 1 or 2 people let alone organize a session with 8+. All that without even knowing if the game would work well through it to begin with. Additionally, Hamachi only allows 5 people within a VPN mesh unless you pay for it, not sure about Tunngle or other software, but to even try this most likely every single one of the people would have to shell out money to buy a VPN solution as well.
All of these issues may be workable for some people but many of them are blockers to even consider trying for others. I for one couldn't be bothered with that much hassle and would rather just play a newer game that doesn't have that BS to deal with. :) For the record, I'm experienced with using VPNs to do this also, so I don't balk at it out of inexperience but rather out of experience.