In the world of screen printing you sell a TON of 18x24 signage, but if you look at the large format industry, the bulk of things printed are 36-40" in one aspect. This isn't to say that you couldn't get by with a smaller unit, being able to rotate your print will solve the media issue, but it won't help the 3x8' banners, which was a staple for me when I ran one.
I have never been a huge fan of print/cut units, it could just be me, but think on this, when you print, the manufacturers recommend your prints rest to allow the ink to set fully into the media Are you just going to stop your printer, waiting for the hours it takes for your ink to cure?
You'd be better served with separate printer/cutter combo. That being said, Rolands have by far some of the best print quality, and VW is a good software package, designed specifically for their equipment.
Mimakis are work horses, I've seen them plow through print after print, give consistent quality, and get through some of the toughest jobs out there, but they don't have the BEST print quality, but is a solid performer.
I'm not impressed at all with Mutohs, any of them. they always seem "thrown together" somehow. That being said, I have clients that love them, but from a technical side, I can't stand working on them, troubleshooting them is a royal pain in the.... well you get the picture.
RIP: Which RIP are you going to use, VW is solid, I used to love flexi, but version 8.6 left a foul taste in my mouth and I haven't had the pleasure of working with 10 yet. Onyx, well it gives great color, but you can't cut out of Onyx, so you need another program, with another program comes a learning curve and a chance to mess things up.
Laminator: You may not think you need it, but trust me, you do. Even if a job is interior it should be laminated for longevity. One of the manufacturers of laminators used to have a saying; The job isn't finished until it's SEALED. It's corny, but true. Lamination takes things from the hobby range of the industry ( *Gasp* he said the "H" word) and puts it into the professional range. It takes ordinary work, and typically makes them look professional, as well as afford them protection from things like fingerprints, dust, cleaners, etc.
SUPPORT!!!! that should be one of the huge keys in your mind, it's all well and good to have a new printer/cutter/laminator/whatever, but unless you've been working on the thing for years, it's going to break, and when that does, who do you call? how long will it take them to get there and fix it? Is it going to cost anything to get them there?
Regardless of what you purchase, good luck