Not to spoil the fun, really, but…
they can't be anything else because of the belt "apron"
In fact, they can. Have a look at
these two guys (taken from
this site), auxiliaries both, "aprons" on their belts, their shields of either oval or rectangular shape. Yes, this may be down to certain standards in depicting "Roman" soldiers. But that's all we have, and so it seems futile to differentiate between auxiliaries and legionaries based on their respective equipment.
It's not clear if they have any shoulder doubling to their mail armour as the cloak covers it.
There are 'short sleeves' recognisable on one or two models (cf the
models painted by redzed, last picture, man in centre), so probably no doubling there.
Anyway, looking forward to your rendition of some nice models.
