Everybody has their own level of skills.....for some, trying to piece this together and then pray it works, is hella intimidating.
I know folks that can strip, bondo, sand, primer, paint, and clear you a whole cabinet, like it was just a trick they picked up reading a magazine somewhere...but they stay 10feet away from soldering irons and pcb's at all times.
I also know folks who are the exact reverse of that.
Besides, if someones gonna mod the case, install and test the cart, AND is able to do repairs if there are problems with the a/b boards you sent them....that's a hell of a service right there.