I might say Keybase, as long as people use their own PGP keys & not the ones Keybase generates.
For chat: Jabber (for OTR), Ricochet, Tox.
Simply for use of the fields: Straight-up PGP key fingerprints! Please. If possible, with means to time-lock them instead of pasting ad hoc messages into the “stake your address” thread. That could solve so many problems.
Keybase users could also post their PGP key fingerprints, of course. But that way, the fields would not be Keybase-specific.
Perhaps also add more fields for extra Bitcoin addresses, to aid transition from the old address format to Bech32. (Of course, there can also be similar issues with PGP. See my signature. Just like PGP2/PGP5 in the 90s!)
If the number of available slots equals two, I would say: PGP fingerprint, plus another “Other contact info” field.
(P.S., thank you for summing your question in terms of security!)