Sorry for the delay on this.
Mamiya 7:
I've used it since 2003 with no repairs until last month, a minor adjustment for rangefinder and film advance end. All purchased used in mint condition.
I've made images about 60% with 43mm, 30% with 65mm remaining with 80mm. I do not recommend 150mm, 210mm.
800 gr body, extremely compact and well-balanced for its film size. Optics are great.
The only 2 factors you may find limiting, is f4.0 or 4.5 aperture and 1 meter minimum focus. Yet HP5 @ 1600 is perfect for this film size, though I used only Ilford PanF+ @50 ASA on my trip to Argentina. Otherwise, it is extremely quiet. No need for 7II unless double exposure feature and brighter viewfinder are needed. I find 7 to be perfectly bright and comfortable as an eye-glass wearing photographer.
If you must go with one lens, I second Pete's recommendation of 65mm. 43mm comes with an external viewfinder that makes the process as focus on the main viewfinder and compose on the external. 43mm is about 21mm in 35 format with no distortion.
Built-in light meter is very accurate with A, AE, manual options, and 10 frame gives you the flexibility to adapt a semi zone system concept.
Do not forget to take the lens cap off as this a rangefinder camera . It gives you the ability to use 10x ND or IR72 dark filters without worrying to take the filter off to compose. That becomes handy on a windy day by the beach if you want to protect the lens, compose and shoot without filter on-off.