It's a little more work on the slab front but it is worth considering sinking the lift in so the ramps are flush with the main floor. Gains you a few inches and makes putting normal cars on it far easier. It also means than any oil spills etc., are likely to be contained rather than going off under benches etc.
You could always provision a drain inside there as well. For other reasons I installed an aqua channel around two walls of my workshop (ground behind them is significantly higher). I've not had an issue with water ingress through the wall because of the drainage work we did in the neighbours yard but it's been handy when I bring a wet vehicle in to be able to sweep the water that drops off into the drain.