I would definitely keep the 100 as my sub 12 and get a mk2 Fac rapid in that case then. Get on the rapid forum. I like The MFR with the shrouded barrel but your limited to a 240cc bottle which isn't massive for FAC levels so I'd get a straight up mk2. Then the world is your oyster in terms of any mods etc.

If you then find you don't use the 100 then flog it. I would of loved a 100 as my FAC rifle but jut heard a lot of bad things accuracy wise (I could have lived with the low shot count and relatively low 26ft/lbs).