Yeer will be building it from scratch ( what a sucker I am) anyway I can't help it it's addictive! i did find some electric legs that will work i will see if i can find them again, they were remote control so all 4 legs raised at the same time. the only issue i see with a slide on is the water tanks, grey water, black water etc, build them in the camper or separate under the truck.
Great news, Ill wait till you start then learn from your mistakes (that's just the kind of guy I am)
Was thinking of doing a small water tank (40L ish) under the sink within the body, already have 100L between the chassis rails
have found out from my travels if your frugal with water it will last
grey water if your in suburbia it goes down the metro drain (caravan parks etc) in the bush I drain it onto trees crying out for a drink (its clean grey water)
Black water well I have a thetford cassette toilet and most towns have the capacity to empty them
and in a slide on where space is at a minimum every inch counts
As far as legs go I agree with Shannon - hydraulic electric pump with a hand pump back up
After having to load my V strom onto the back of the truck by hand because the electric winch relays were full of the Pilbra and knackered Ill choose oil over lecky jibbers
after all the stand by system to electricity is handraulic.