A few years ago there was a guy on here who showed us how he took flex track, cut it into sections in various lengths of curves and straights, glued it onto cork roadbed and ballasted it.
He then joined it with rail joiners. So he had the look of ballasted flex track but it was portable like roadbed track.
Except then it wasn’t flex track any more, just really nice looking sectional track.
Maybe with research and work it is possible, but that doesn’t quite get there.