Sorry for watering down you a bit but indeed there is a marine model with a proper sniper rifle. It's the tactical version of the codex scouts.
Here it is having the missle launcher but they have exactly the same weapons of the scouts, including the sniper rifle. They have the Mark IV armor though, so a FFE edition is needed to replace the helmets by another variant in case of more uniformity.
I don't know exactly who made them but they were included in Eternal confrontation mod (called recon marine, which is completely made up).
Nice catch man! i didn't know about that at all! Well,I will keep working on mine as a way of practicing FFE and kit-bashing.