...... One could easily find a builder that will custom build to your specs and requirements. You then will have a rig perfect for you. ...
I would push back a bit on that angle. anyone who has ever had a haircut, suit altered, or home improvement project done, may also agree with my thought. or not.
finding someone to carry out your instructions, even though most job descriptions have the inclusion "ability to follow simple verbal and written instructions" is hardly easy. and through the entire process that person will know more than you do about what you want & need.
who will, and at what cost (gawd help me if the engineer found out I used the word "budget") both monetary and in time, write the specifications for the job? as soon as the purchased agrees to provide either, the scrimmage line is set and the game is on. extras & change orders become the battle du jour. the buyer then needs to be engineer, craftsman, electrical & IT expert ad nauseum. and he has to watch over a disgruntled bunch of "trained professionals" most of whom "don't need no pretty piece a paper" to do excellent work, build his dream?
we all know craftsmen, both full time pros and weekend warriors. but how much would we trust them to build a multi-thousand dollar life-may-depend-upon-it vehicle? when you're out in east gagordia and the damn thing won't turn over, is the custom builder going to leave his family picnic and come to get your butt out of a hole?
I could go on . . .