The bike lift is the biggie though. The scissor action has one set of legs rolling fore and aft. Dont want a 965lb touring bike 4 feet in the air if it aint stable.
That part of your shop is an entirely different matter. I have a lift in my shop and was concerned about stability (OCD overkill, I know). The base plate was half-inch steel, so I butt-jointed and welded larger pieces of half-inch plate to increase the footprint and bolt pattern. In retrospect, that almost certainly wasn't necessary, but I never worry about getting under a car/truck/tractor/piece of equipment.
Again, in my case, 'leveling' wasn't an issue. I wonder if you could mill some plate steel at an angle to fit under your lift's base plates that would orient it at vertical to the floor? Perhaps you could then weld them to larger pieces of plate like I did to increase the footprint; maybe add some gussets or bracing to the uprights; and weld bolts to match the stud pattern on your lift? That might help with the restriction on no driven floor anchors. Probably not on the radar screen, but an added advantage may be that the lift also becomes mobile.
I have no idea of the dimensions of your lift, but probably the safest option would be to get a full-size sheet of 1/2" or thicker plate steel, weld some studs to it, and mount the lift onto that one solid piece. My local source for steel told me some time back that cold rolled weighs 40.8 lbs. per 1"x12"x12". According to that formula 1/2" thick 4x8 weighs 652.8 lbs. My main (stationary) work bench has a top made of that with legs and bracing made of 4x4 square tubing with 1/4" wall, plus a 1/8" thick shelf. I did the math some time back, and the whole contraption weighs around 900 lbs. I wouldn't hesitate one bit to mount a lift onto it and put a motorcycle on it.
The biggest challenge for you would be getting it into the garage. (I had to weld homemade casters onto mine in order to move it to another part of my shop, then cut the casters off of it. It's mighty sturdy.) But the way I'm visualizing it, you could actually do the build on site. If that's not big enough, it's my understanding that you can get cold rolled in 5' x 10' sheets. That would weigh in at over 1,000 lbs.
Cold rolled isn't cheap these days, but if you buy it, you own it. If a move into your own home is in your future, you can always re-purpose the steel.
Good luck.
Regards,
Terry