[@golani] I'm more interested in creative storytelling than I am in the minutiae of what is and isn't on the horizon, so realistically if you wanted to mix and match to your heart's content, I'd say go for it. But for the sake of uniform writing... let's just say biplanes are a thing and tanks haven't been invented yet? We'll put a hard stop at 1914 as far as the technology is concerned.

Like, the stat numbers will determine how well you do things, but if you'd like to have a Wyvern based air force that throws bombs or biplanes with mages that chuck fireballs, go for it. Just know that the numbers for stats will determine how effective things are.