My crawlspace is almost tall enough to sit-up and I didnt have any issues just picking it up and moving it where I wanted it. I tried to keep it upright so the oil wouldnt do anything weird in the compressor. If it was a small mansion under there and youre wanting it in the far corner, I say the sled idea sounds like a winner.
I must say, I love having a dehumidifier in the crawl space. My house is old so it isnt sealed up the best, but the humidity stays right around 50% year round now. I have good plastic under there, but its not sealed to the block. During the spring and fall when the A/C isnt running but its raining outside, my indoor humidity would creep up near 60%, which I imagine even a tight house would do. Any house I have with a crawlspace or basement will have a dehumidifier from now on. Same with my garage, I try to keep it in the 50% range.