Sadly I don't think there is an easy way to make T3 air more engaging/less oppressive.
Slightly delaying T3 air (by like a minute) and/or increasing its cost wont change the meta really, it will just delay ASFs a bit and make both side's ASF clouds a bit smaller, but you are still heavily incentivized to rush them as the only counter to your opponents ASF are your own.
Heavily delaying air (by more than like a minute) and/or increasing its cost will change the meta, but only to the much more toxic T2 bomber all-in strategy described by FTX, now being forced in every game.
(Honestly, my gut instinct is that if you had two decently competent, coordinating, try harding teams on both sides of every match with the current balance, T2 bomber strategies already should be pretty oppressive on many if not most maps. Imo the only reason that they aren't is due to the missing coordination/try-harding.)