You're going to get a million answers, and I admit I skimmed your long post, but yes the Mamiya 6/7's are expensive but have perfect glass! (Mamiya 7 II owner with 43mm, 65mm, and 150mm lenses).
However the RB67 / RZ67's are also great! (RZ67 II owner with 50mm, 90mm, and 180mm lenses). The Hassleblad guys will always say their lenses are better but the fact of the matter is both are similar in quality, and the Mamiya prices right now are GREAT so it's like getting a Hassy for 1/4 the price. So I support looking into an RB or RZ system.
Again I didn't see your price but I got my entire kit on eBay for around $600 if I recall.