Upload & Sell: On
Sub-100mm should be fine. Most of the R lenses have M-counterparts that are better performers than the Rs. The 15/2.8's the only exception I can think of, and it's pricey as it stands. Otherwise, unless there's some advantage to the adapted R lenses that I'm not considering, there's really no point in investing in, say, the Summilux-R 35 when the going rate is comparable to a pre-ASPH Summilux-M, which is a lower-contrast lens but doesn't have the CA, vignetting, and visible distortion of the R. The 80 lux might get a bump since it's unusual and cheaper than the 75 lux.
I'd say the big targets will be the 100mm APO-Macro, possibly the 60 Macro, the zooms, and the longer teles.
Speaking of which, I've got a beautiful copy of an APO 280/2.8 (non-mod) up for sale on trade on the boards, if any of you future M owners are interested.