I think that's fair enough: without options, I think we can improvise (especially given that at that scale, uniforms that are "close enough" are easy to fudge, if the helmets and any distinctive weapons are close enough to "sell" the illusion), but I'd rather have options, especially accurate ones, if practical! (And the Arditi in particular are definitely going to be tough to improvise on.)
And yes: the Partisans absolutely need a little creative kitbashing around the wealth of SMGs! We could definitely use more weapons that might have been available to civilians before WWII, to really balance the kit out for earlier eras, and that sort of thing would still be useful for WWII: revolvers, shotguns, hunting rifles, surplus arms from earlier wars, and the like.... I don't know what WA has planned for "Partisans II" and beyond, but "Partisans" for other conflicts in other times times and places would definitely be something I'd buy.
Maybe the Belgians should be considered, too - I supposed the French kit might be a good start on kitbashing them, but the Belgians actually had some pretty distinctive uniforms and hats, it seems - so:
- Belgians - fairly distinctive uniforms; you might be able to substitute the WWI French torsos and forage(?) caps, but it's not a very close match from what I can tell
- Bulgarians - fairly distinctive uniforms; you would, I think, be able to fudge somthing from a hypothetical WWI Russian kit
- Greeks - might be kitbashable, with a little fudging - in some pictures I've seen, the uniforms don't look exceedingly different from the Germans (though I have seen other pictures with a rather... unusual shoes-and-tights combination - they might thank you for subbing in something else!), and a few soft flat caps might be sourced from the French Resistance, or perhaps from the WWI Germans or upcoming WWI British kits; the Greeks apparently also used French helmets, the delightful Chauchat machine guns, and Manlicher rifles and carbines, so the French WWI kit might come in handy for kitbashing!
- Montenegrans - might be kitbashable, with a little fudging - the uniforms don't look very far off from the Germans (and it looks like the Serbians, as Brian mentions, would probably work), and those soft garrison/overseas-style caps might be souced from the French Resistance; the Montegnegrans apparently also used French helmets, the ever-amusing Chauchat machine guns, and Mauser rifles
- Portuguese - fairly distinctive uniforms; at a stretch, you might be able to fudge some WWI British torsos and brodie helmets, the bluish-grey colour the Portuguese seemed to use for the uniforms might help disguise the British origin, but this is probably not a very close match; the Portuguese apparently did use some British SMLEs, Lewis guns, and helmets, as well as Luger pistols and the almost ubiquitous Mauser, so the British and German kits would come in handy for a kitbashing for a rather interesting and unusual subject (I don't think I'd ever thought about the Portuguese role in WWI before!)
- Romanians - you might be able to kitbash something out of German torsos, French helmets, and French rifles (as a really rough substitute for the correct Mannlicher rifles) and outrageous Chauchat machine guns; the Romanian caps, however, are quite distinctive - I'm no expert by any stretch of imagination, but I'd be surprised if you'll find anything like them outside of a proper Romanian kit!
For kitbashing, I'm not paying very close attention to the officers or gasmasks in these armies, though - at a glance, many of the officers in particular had some very distinctive, odd, and probably hard to find uniforms, so good luck!
Otherwise, it looks like the WWI French and Germans were a great place for Wargames Atlantic to start, for providing bits for kitbashing projects, and I'm thinking a Russian kit might be a good next step, now that I've seen how closely the Russian and Bulgarian uniforms resembled each other; Russian bits - helmets, caps, rifles, pistols, etc. - would surely come in handy for this sort of project, too.
That said, a proper, dedicated, historically accurate kit for these "minor" power armies is always better than improv and fudging with other kits, wherever economically practical :)