I recently down-sized from a 14' to a 13' raft, but kept my NRS frame and other gear. It is a 60" (wide) compact outfitter frame, and I cut the length to 70", from 78". I like the flexibility to rig it differently for various trips, and for the last year, it has exclusively been car portable, so some breakdown is necessary for me. I have used plywood side board decks on it, but they are less important to me now. I have appreciated double-rail frames on larger boats (rented), e.g.,on the Grand Canyon as they have longer spans and heavier loads, but don't really see the point on mid-size and smaller rigs. If I was starting from scratch, I would like a bent and welded perimeter frame with a NRS standard width that I could use their crossbars and accessories on, or custom as needed. Unfortunately, that sort of locks you into lo-pros, but you would only need 4 for a 3-bay. I like, and have used speedrail 5E, but they seem less flexible for partially welded frames.
If cost is important, you can buy speedrail fittings on ebay, about half price, and find some used oar stands there, here, or CL. Put the savings toward a custom AAA footbar, I love mine, and it also provides one crossbar.