Mr.G- I think this is the case you could make for a Ftr/Arm/3 Inf on R1. A Ftr is the same price as the two Arm you’d normally purchase. You’re losing 3 pips on offense, 2 pips on defense, and 1 casualty. But you’re gaining a unit that doesn’t get exposed to destruction when used, and has great range for the rest of the game. It can also provide spot duty to help defend other allied locations.
I personally never buy one unless I’m playing a newbie, because I think the armor is a better all around purchase, but I think as the game goes on you’ll be happy to have the extra fighter. More than one fighter purchase should be exploited by a competent allied player, however.