The Voigtlander R4A/M models have viewfinders specially set up for wide angle lenses. If you don't want longer focal lengths than 50mm then they're probably your best option. The occasional use of a longer focal length can be handled with a supplementary viewfinder, also from Voigtlander (Cameraquest).
As for the rangefinder base length issue, it could be argued that it affects long focal length lenses (most people can't see the difference) but is not apparent at closer range.
I use an R3A and the 1:1 viewfinder in that case is just brilliant. I got a +1 diopter lens for the viewfinder to help my old eyes and am more than satisfied.