UKF vs OST: Getting my arse handed to me

Yo, so I'm an experienced player, I have upwards of 2,000 hours, the majority in UKF, and in the group I usually play with am placed top 200 on the leaderboards in team of 3 (last I checked anyway) but mostly play 3v3s and 4v4s.

Recently however, map dependent, I have been getting absolutely demolished by this one Ostheer strategy. It beats me every time and I'm left floundering with units with no vet and no armour.

So the strat:
The strat is essentially inverting the usual, so using infantry AT backed up with machine guns and Anti-infantry tanks. Last I faced this was today in a 2v2 and the guy was using 3 squads of Panzergrens with Panzerschrecks backed up by an MG42 and a bunker, with a PaK40, then for tanks he had 2 Ostwinds and later on, a Tiger 1.

It essentially completely zones out my infantry, I couldn't sneak flank them with commandos due to the ostwinds, and my tanks, even churchills, couldn't get close to kill the MGs so my infantry could push in. The guy ended up killing my churchill and my firefly by stunning them both with a frag bomb run and pushing them with the panzergrens (I was fighting at the edge of the map so the bombs hit me immediately as the flares came down, I didn't just sit in them)

The issue essentially boils down to me having no mobile indirect fire with mortar pits being unusable due to the fact if he moved up his units, I would have to retreat leaving the pit to be destroyed. The one unit that I have beaten this with is the land mattress but I don't currently have Mobile Assault slotted. I've fought it before by borrowing a teammates pack howitzer and priests too.

Aside from slotting mobile assault. I was curious if anyone had any suggestions? Like I said, I'm an experienced player, but I'm completely stumped, it beats me every time unless I was to take mobile assault (or I guess royal artillery) from the start every game, 2 regiments I'm currently not using. The only other thing I can think of is building muntions caches early and spamming Tommy flares at him all game.