Sounds very complex for a simple job.
If you are, in fact, using "plastic ramps" why not drive the car up on those? Backing up onto ramps isn't hard. You can remove the undertray with the ramps in place.
If removing the undertray takes so long that the oil cools, just start the car up again while on the ramps and let the temp come back up.
Also, you don't need to remove the wheels to replace the transmission fluid or bleed the barkes. I do it just using the ramps and working on the brakes from underneath. Very easy.
'05 Elise Magnetic Blue, Black, Touring, Hard Top, Star Shield, Stage II Exhaust, Arqray decat pipe, S2 Front Splitter (UK), Sector 111 Rear Tow Hook, Driving Lights, Cup Airbox, Shift-I System, LSS Dampers & Springs, Sector 111 V-Bar, Schroth Profi II 5 point harness, Exige S Probax seats, 1/4 turn undertray screws, Stealth bulbs, BWR SC with PES tune, Innovative engine mounts, SS brake lines.