Altamont would be a great spot to cross the Coast Range - for commuters from Stockton, Tracy, and Modesto/Turlock. HSR through there doesn't stand a chance, though, because it would have to be underground throughout the Livermore Valley and Fremont/Milpitas and would need a bridge over the Bay (the existing Dumbarton train bridge isn't adequate in any way). If you're trying to build a high speed line that provides even a little timely through service to LA (some day), Pacheco makes more sense (fewer stops and more construction options), though it does transfer the long-distance commuter effect to Fresno which really isn't prepared for it.

Altamont does need improvements. A future, improved version of ACE with an in-station transfer to BART, that's not just random conventional commute trains on UP, will fill the main need there. Regardless of political connections (and one of your unholy crew is retiring soon), BART makes no sense for a Central Valley commute - doesn't go, without transfers, where most of the people want to go (Silicon Valley) while ACE does. And San Joaquin County is both outside of the BART district and willing to stay that way (ACE is locally controlled/managed and they like that).

HSR doesn't have to be only one line, and shouldn't be if it's to serve transportation purposes rather than just be a monument to somebody's political clout. It needs to be a system, using separate tracks where appropriate to bypass freight and urban congestion. As a practical matter, though, that can't happen in the lifetime of most adults of early middle age or more, so I don't worry too much about it.