I think the easiest way to allow multiplayer games is to remove the turn-limitation of the demo...
I know I played a lot of them before my full copy of Dom I arrived. The research cap (and the fact I loved the game dearly) were enough for me to purchase it for good after a week intense playing.
I'd love to show around Dom on one of our bimonthly LAN sessions as well, but I can't afford to purchase the five to eight copies required for that.
