Would
Smile succeed as a 1975 album is a very interesting question. Imo it certainly had part of that oldies vibe which was so popular in the mid 70's. On the other hand it is the product of the psychedelic age which lasted from 1966 to 1968 (at the latest). Especially in the department of psychedelic pop and baroque pop. Psychedelic rock would continue into prog rock and remained popular for the rest of the 60's.
I believe Smile's best chance of doing it good would've been the initial release. Hype was high and the time was 'right' for the type of music. Smile would stand out sorely in 1975 both in production and sound
. It was the sound of a bygone era of Sgt. Pepper and summer of love. However since ES had come out and BB's were popular again one can never know. Maybe it would've gained some traction after all.
Landlocked: nah, can't see it happening. Tracks are too inferior. They probably recognised this themselves at the time that these leftovers were not sufficient.
1975 new album: had a good chance, but it seems the band never really got together to record a new album and instead focused on profitable touring.
Many of the suggested tracks would probably do well on such an album but there were no real hits beyond maybe It's OK and to a lesser extent Good Timin and River Song. Would be great to see if more tracks from this poorly illuminted part of their career will emerge a la Barnyard Blue (pretty solid track imo).