Playing Devil's Advocate....and also having had both kind of rigs......
A 3 tier has some pro's a lot of people may not realize......
If your bk burner is low profile, your "staircase" won't go extremely high. as long as the ball valve of the next vessel up is 2 inches higher than the max fill of the lower vessel, you should have more than enough gravity/siphon. If you use a modified footprint like this:
1550 - 10 Gallon Tippy BrewSculptures | MoreBeer, you have the best of both worlds! I'm finding more and more that gravity is awesome. I spend a lot of time screwing with my march pump (yes, I know how to prime it
). Also, I realize with a sight glass and thermometer, that I don't look into the HLT. As long as it's high (a few inches out of sight on your toes), but not TOO high (towering over you, like 8' in the air) and it's secured, you should be fine.
3 tiers aren't terrible as long as you keep the MT and BK well within workable height. Oh...also consider supplying your hlt with a fixed water line or shepherd's hook so you don't have to hoist the water up there. IMHO, a site glass is a must in this setup.