RE: NYP-ALB electrification, one thing to keep in mind is that with MNR owning the ROW between Spuyten Duyvil and Poughkeepsie any electrification extension on Amtrak's part will have to be approved by them first. Doing away with the 3rd rail and replacing it with catenary would require MNR replacing a large portion of their 3rd rail EMU fleet with dual mode EMUs akin to the M-8, M-10 or whatever would be in service at the time). And north of Croton-Harmon Amtrak would need permission from MNR to install the catenary poles, substations, etc. (assuming of course that MNR would have NO interest in extending the 3rd rail farther north).
As for NHV-SPG remember that Amtrak and ConnDOT have 100% control over the line (with the exception of the approach to SPG station) so they can do whatever they please with that particular corridor.
Other than that it's just all a matter of coming up with the dough