Given Woods Hole area residents' perennial complaints regarding ferry induced traffic, (and by extension Falmouth residents) would it be at all likely that they would be less NIMBY-y towards reactivation, especially in full even through non-formally landbanked portions if it meant that it would divert car trips?
Especially with the SSA/CCRTA MOU, personally I do think a Boston- Islands Ferry timed transfer service, with bundled tickets, is an amazing idea as an service option for the capeflyer, for which, if the capex isn't horrendous, which it shouldn't be to rebuild a couple miles of track, a direct walking transfer should be much preferred.
However... Isn't the bottleneck the rail bridge? I seem to recall some discussion in past years about an expanded capeflyer schedule being stimied by the USCG refusing additional closings. That bridge is also close to 90 years old, and I don't think you can raise it substantially either.