I have in the past mounted a small desk on the top of a rolling rack: IMO it is a bad idea for several reasons.
1) For starters the risk of shock damage is greatly increased when transporting.
2) The size and weight of loaded combo cases is a major problem.
3) My SQ5(with it’s dust cover) a DX168 & a Glyph Studio external HD fit snuggly in a large Gator suit case for safe transportation.
4) I loaded a 8U SKB case with an Atlas ECS-3 power sequencer along with an ETA-20SH (dedicated 20 amp sequenced power for speaker
stacks) along with my Masterlink HD (that I use for providing back up tracks)
5) I had a real 3/4 inch piece of cabinet grade plywood that made dandy templets for stabilizing the SQ5 on top and the rolling trey on
the bottom of the SKB case.
I provide up to six tube mics with stands, a KV2 EX10 wedge monitor and all of the requisite cables for on stage deployment to FOH. Appropriate packing for each of these elements along with a a pair of ES10 speakers for mounting on K&M tripods for small gigs, a Two camera video system and a D-28 guitar in a Leaf case fit in the back of my SUV. When I need to provide my KV2 ES large speaker stacks my Ford Expedition SUV has no trouble pulling their trailer.
Given the better than decent custom SR installs we generally deal with today, transporting FOH stacks is rarely needed so our stage front end gear is all we usually transport: unless we are dealing with a venue with no/or very poor existing SR. We all have specific needs that will largely determine how we choose to package our gear. In my situation flexibility is paramount.
Hugh