There have been proposals over the years to relay the B line but they have never gotten anywhere. Ditto for a conversion to trolley bus, which would have the advantage of vehicle storage at Geary Carhouse aka Presidio bus yard. Muni seems to have put a moratorium on any further trolley bus conversions out of fear of not having enough diesels to cover emergencies, etc.

The subway idea goes back to the 1937 bond issue, which failed, I believe, due at least in part to the opposition of the Market Street Railway. Too bad as that would presumably have saved the B from Urban Removal in 1956. A subway surface operation, in tunnel from the Cathedral Hill area to downtown represents the middle ground. At the other extreme is the BART empire which wants broad gauge in tunnel all the way to Ocean Beach. Needless to say the Richmond district would never be the same.