Indeed and there's only the Legion and Regulares that are actually specifically 'Nationalist' strictly speaking, the rest of the bunch can be used within a Republican army, time and place excepting. It's somewhat true vice-versa of course, but to a somewhat lesser extent.
Not to detract from it being a great range overall in any case, but for me it's an obvious hole within it.
Obviously I won't argue against any other additions to the range too, whatever they are. Engineers, stretcher bearers and medics would be especially welcome... I'd even pop for an artillery limber and horse team.
To be honest though, whatever came out wouldn't be enough and I could always say "But what about...?".