After looking at the Trek that on the lot at my dealers lot... I'd like to throw out a couple of suggestions to be picked apart (improved upon) if someone actuallly wanted to retrofit a drop down solution...
My first thought was to mimick the Trek system and go with a rack and pinion system... But, finding the matching parts is provong to be the major stumbling block with that idea...
Then I thought about two other systems...
The first was a similar system to what they use on boat lifts... Basically it's a single electric motor with two shafts (the motor drive the two shafts via a belt) and the shafts are wrapped in stainless cable... (the weight of the boat helps to lower.) In a MH a track, would need to provided to guide the bed down...
The second system would use a garage door opener mechanism (converting the motor to 12V of course...) and a screw drive to lower the bunk... All the needed parts are there... the travel limiter switch, the screw reciever and the track...
Granted, both would need a bit of "shade tree" engineering... but it's a start...
If the bunk is going to be hinged at the front of the cab over section that the boatlift shaft arrangement may be the best arrangment and the easiest to backward engineer...
Just my .02