It is possible to make a VF14 replacement tube in a glass envelop, there has been a huge advancement in material science since 1958. But will the market take it up as good enough? That is the difficult question.
If every specialty point of the VF14 is replicated that matters, there should be no problem with a glass envelop, but even making a tube like that is a challenge, the current manufactures are unable to do because nobody has the machines left to make double helix filament.
Sovtek/EH/Reflector started to make spiral filaments a few years back to get better hm rejection, but it is in the end a single Helix filament.
Also the gettering process of the steel tubes was quite unique compared to the standard ring getters. So many points to talk about without getting to a real comparison, unless a tube like that is made.
Best regards,