I once did a stupid game as Britain where I focused entirely on my airforce and left my land army barebones…basically, called Germany’s bluff on Czech, and when I entered the war on their side, just obliterated their airforce and bombed their mils civs and airports to dirt. Actually worked pretty well, Germany cant really break Czech’s forts unless they have stupid amounts of CAS damage, which they cant reliably do if youre shooting them out of the sky and theyre dedicating a chunk of their own fighters to stopping your bombers. I did get lucky that the democratic civil war event happened though.
This was pre plane designer so I dont have any builds, but I would guess that maxing out bombing stats, then air attack stats, then air defense stats in that order would probably be the most beneficial. Could be wrong though, sometimes the math is messy.