http://www.moddb.com/mods/mass-effect-dawn-of-the-reapers Someone has already started a Mass Effect mod. Perhaps you should consider collaberating and working together?
JediExile
[quote who="Nicorius" reply="21" id="2539069"] And Omega could also be a planet but on the opposite side of the galaxy and capturing on of them should give a bonus to your empire. [/quote] While this would be a great idea, it would seem more reasonable to make Omega the pirate base (assuming we choose the mercs as the pirates.) As it is stated that Omega is essentially a pit of lawlessness.
so attach the map to the mod itself.
Relating to the Mass relay network, what about the Omega-4 Relay? You could research the Reaper IFF, & go to the 'center of the galaxy' to destroy an AI Collecter race. They could be the pirates sice according to ME2 they only have 1 ship design & one Base. But we'll have to wait till ME3 comes out. (Sorry for spoliler >