Just an idea but I think it would be more realistic if there was a bigger difference between an aimed and a snap shop in terms of both TU's and accuracy. A snap shot should be quite cheap to do but unlikely to hit anything from a distance - i.e a shot from the hip where as an aimed shot should (as it is at the moment) cost most of the turn and have a far higher chance to hit.
At present a new solder can obtain near 100% hit chances at the max weapon range whilst sniping which feels unrealistic.