I've been thinking about trying this for a while now, but I didn't want to jinx it until I was reasonably sure that it could be possible. Today I bought a used 245/70R17 tire and mounted it on a stock rim and test fitted it, front and rear. It rubs, but not too terribly. I think this might work. I'll post more pictures below.
The tire I'm using to test: (all info from DiscountTire.com)
(used)
Cooper Discoverer AT3 LT
LT245 /70 R17 119S E1 OWL
Diameter 30.55"
Weight 44 LBs
Load Range E1
Stock wheel:
17x7 +55
The Car and relevant mods:
2020 Crosstrek Premium
2" Rallitek Lift Kit (strut top spacers with rear subframe spacers)
Ralitek rock sliders
Primitive Racing skid plates
Current rubbing in the rear is only the front of the wheel wells. There is a little flexible mud flap thingy that will have to come off or be relocated forward. The rear plastic on the side skirt will have to be trimmed. That will be a little tricky since the side skirts are sandwiched in by my rock sliders. I ordered a cutting wheel for my die grinder to help with that. Removing the rock sliders would be an annoying undertaking.
Rubbing in the front is also not too bad. The front corner of the tire rubs a little when turning, as does the rear corner. I had previously moved the front of the wheel well liners forward about an inch by drilling a new hole in the bumper and moving using the OEM plastic clip to secure the liner that much farther forward. I will probably need to either trim off some of the ribbing, or heat it up and try to bend it forward.
It does look like I will want to trim the plastic rear of the tire, or else it will rub badly when braking and turning. I have previously trimmed that part on the other side as a test, so I know it's not too difficult.
I forgot to take pictures of it on the rear.
Pictures of the front passenger: