1 & 2. If you only have the MH and want to go see some nearby sights you have to break camp and take the MH. We stay fro several months in an RV Resort near San Diego and I see this all the time. A Class C will pull in they setup camp and then the next morning the father is un hooking the electric, sewer, water and cable, puts away the awning and they hop in the MH and head to Sea World for the day. When they come back to the site he has to re-hook up everything.
3. Levelers and Blocks will make this a non-issue.
4. Alternative is a portable generator. You can get a Honda 3000 equipped with a key fob remote start (not from Honda but from an online source). It uses gas not propane so you need to carry a small gas can for refills.
I would first rent a MH to try it out... Going from a 40 footer to a smaller unit will take some adjustment in living style...especially with only one bathroom. Think about being stuck in a 25ft MH if the weather gets bad and you have to stay inside for several days. I'd much rather be in 40 ft than 25 or 30 feet.
I bet you'll find there really isn't much difference between a 40ft 5th wheel and a 25ft MH in terms of manuevering and parking in spaces. Both take some practice to get used to. We have a 38ft 5th wheel and have plans to go bigger for more comfort. Our next will be at least a 40 footer with two additional slideouts.
The 5th wheel allows you to use the tow vehicle for those sight seeing trips.