At the very least you'd think LACMTA would seek a dispensation or indulgence(not quite sure which is ecclesiastically correct in this instance)from Jerry and the Sacramento curia to try out triple section buses. If there is a physical impediment to that then it would seem there would be an impediment to light rail.

The only other bus op that I think of that would involve so much civil works would be a trolley bus subway in the downtown portion of SF Muni #38 bus line. Somewhat longer than a mile and of course vastly more expensive but with a much larger patronage as well. Not as much capacity as light rail but avoids war with the outer Geary merchants and could handle some tight curves that might be necessary south of Market where skyrises have taken over in recent times. If your future light rail were lo-floor, conversion from bus would be facilitated.