A 36" grill is plenty if you're cooking 5 burgers at a time. a 36" grill is plenty if you're going to have one person tending the grill and he/she can only handle 36" and you're cooking one item only (all the same temp). If you're going to need multiple cooking zones, then a 36" grill can get small pretty quickly, especially if it's your only cooking station.
As for the glamshell style grills (and I've only seen the griddles in a commercial environment), to get good transfer of heat, you have to have good contact between the heat source and the meat. The only way to accomplish that is to have some "squeeze" on the meat.
If your point of differentiation from the competitors is better food, then you have to make it better. Shortcuts are how the big chains do it. They figure out the science behind getting the best results with the fewest variations. This does not mean the BEST results overall, just the best they can do, given the limitations they're willing to accept. Heck, McDonald's turns out a pretty decent burger for something that's cooked, held, and nuked to order. But is it truly the BEST they can do -- of course not.
You can't substitute a different patty in place of what McDonald's has now and come up with as good of a burger as you could make with the same patty using better techniques.
Also, you're not going to be able to afford daily meat deliveries unless you do a killer business. Most food suppliers won't "stop the truck" for less than a certain dollar order. It may be as little as $250, or $400 plus. I would also suggest that you may want to actually hold your meat for some period of time after seasoning but before grilling.