The only drawback with the legion is that they wore their shirt open as a matter of pride (they were the only unit allowed to do so), even when wearing the tunic. This might create more of a modelling workload than the fact that they have the right webbing. I'm not sure whether they followed this tradition in cold weather as much though.
The Lee Enfield was used in some numbers in the SCW, it was one of many assorted weapons supplied by Russia, along with Lee Metfords, Mannlichers etc. Unfortunately the Nationalists didn't use it. There is bound to be someone out there who does seperate Mausers surely?