Airmobile forces have used light tanks since WWII. Hence the Tetrach and the Locust. They were light, fast, and pretty much useless against any existing tank.
However I think APCs/IFVs have a role in LAMI forces or forces operating without fleet or other air support. Any world with highly unstable weather and very high winds, or large amounts of AA, or large cloud cover (particularly of anything inimical to flight surfaces) or huge flocks of birds (BIRDSTRIKE!!!) or that is too low priority to rate a fleet presence, would be an argument for APC/IFVs.
Basically I'm thinking something similar to the APC from aliens. Deployable from a Viking (I think I'm remembering correctly) and able to carry a squad of LAMI (but exosuits won't fit in, and PAMI only at a push) with some anti-infantry/light anti armour/big bug capacity and basically used for tooling around in and fire support.
What would happen to Skinnie etc worlds the MI capture? MI are too valuable to stick on occupation, whereas LAMI would need something to patrol in.
I agree that getting the system resurrected first is a priority, but a very well sculpted LAMI APC would be a next step. The current design (from the MI equipment guide) is horribly ugly though.
So a no to true MBT, but a yes to a utility APC/IFV. Like a Warrior or Bradley, but in the future man.