You are going to have to fill in a few things with metal, possibly WW1 Austro Hungarian ranges (or WW2 ranges).
The Hungarian Light Machine gun look just like an MG34, but fed by a curved box magazine on the left side of the gun.
en.wikipedia.org/wiki/MG_30 that could be an easy mod in plastic
The Schwarzlose was the standard MMG, a Maxim will do at a push, but the cone "accelerator" is a must (And note the rear housing).
link
Their sub machine-gun is interesting, almost beretta like profile as well. The Magazine folds forward a feature liked by troops as with the standard rifle being a short Manlicher, NCOs and specialist were not distinguished at range link
As you can see from the image in the article, it is a relatively large weapon, so you can probably modify a rifle for that
The close fit of the trousers below the knee could be replicated by a paint conversion of the puttees of a Late WW1 German in puttees, or trimming a little away from the classic jack boots.
2 helmets seemed to be in service, the (then) Current issue German helmet, the typical WW1 German style helmet and in very small numbers (small enough to be ignored), the WW1 Austrian Berndorfer. So a mix and match approach would be suitable.
Late war, they adopted their own Zelt (and unique cammo pattern) and some issues of the trousers became baggier (so late war Germans can be used then).