Well but nowadays, with gazilions of GB of ram, 4-6 cores, 100Mbit outputs, etc. there's no much problem running some servers at the same time, in fact Korrea's server has been hosting 5 simulators at once with success for years. At the end, DCS and FC2 have different licenses so those are different products and should be a way of running both executables at the same time. Perhaps through different users/sessions?