Allies already have that in the form of nondoctrinal recon planes, at least for USF. Given that one of these planes comes from the opponent's base sector (At vet), it's similarly nearly uncounterable in practical terms.
It's also worth stating that only Soviet opponents will have artillery vulnerable to such a flare, given that USF and UKF artillery are mobile vehicles, not emplaced guns.
I think the recon tools of a lot of factions need a lot of fiddling with.
There is no magical thing called "allied factions" that has it all.
Talk specifics or stop talking about nothing.
USF having major recon is NOT an excuse to be salty about soviet flares.