KDirect:
It's all about automation and doing things the right way. I run a shop with 10 M&R Autos, and we have multiple 14/16's and an 18/20. All are Tri-Loc compatible, and because we also have two Kiwo I-Jets, our screens are basically pre-registered.
My crews can get any job set up and printing in less than five minutes a screen.
Having a larger press means we can print more colors certainly, but sometimes we have three flashes and cool down stations for doing complex jobs, such as simulated process art, high density, multiple metallics, etc. We aren't limited and can print basically anything the art staff can dream up.
I've got a great Pinterest board that I use to show clients and others around the shop since most of our clients are somewhere else. Check it out:
Behind the Curtain at a T-shirt Shop
These presses are very expensive, but you can find some good deals on used ones. I would recommend tailoring your business plan to use equipment that fits your demographic, and if you come across a job that requires something you don't have just contract it out. You can still take the job, but you'll just make less margin.
Good luck,
-M