Can't they bid back into the RHS again if they're that dis-enfranchised at that stage?
FWIW I do know of at least one very well thought out voluntary LHS to RHS on the
same fleet. However it was a few years ago, before pensions and tax got so complicated and was done very late on in the individual's career.
I think doing it these days, and in mid career, would expose the individual to the sorts of financial penalties that GS-Alpha has highlighted .