Sounds reasonable. Would be nice to get some spectroscopic evidence of water, maybe even before looking at light curves (??)
On the other hand, just because a planet is within a zone which might now
allow for the presence of liquid water, doesn't necessarily mean that planet actually
possesses liquid water, though, eh? Let's face it, the environs around a WD have been through some fairly extreme conditions in order to get where it might be today (ie: un-water-friendly). What sort of probability figures can we assign to the presence of water (in any form) for WDs?
This idea of post WD planetary formation (or capture) might also a bit of a wild-card (read 'stretch').
On the other hand, it seems that every star has been through the protostar phase, where it now appears, is when the water is initially formed. (The latest discovery of huge water jets from
L 1448-MM is one such example). It seems that Earth may have captured most of the water within 1AU of G2V ... but that's about all we presently really know.
Would water molecules linger after a star has gone WD .. that to me, is a key question …
Good idea to go looking for it all, though.
Cheers