I’ve done a bit of research. From what I’ve discovered, I would definitely choose a 2-post asymmetrical lift, since it allows opening the doors with the car on the lift and allows access to the entire bottom side. The down side is that it has to be anchored to the slab, and if you don’t know the slab thickness or compressive strength, this can be a problem. I would probably buy a Rotary Lift–you can get a 7,000 lbs. capacity lift installed for right around $4,000.
By the way, I like your storage facility idea, primarily because it could foster comradery and sharing knowledge about maintaining the E30. If I weren’t planning on building my own garage with a lift, I’d be tempted!
Sasha