P.S.
SHA512 probably would be the right thing. If someone's too lazy to compare such
a long fingerprint, he can still choose just to compare just one half of it.

Sure, a standard for that would be great.

MD5 is pretty much broken for security purposes and I would wonder, if that's
not also true in the context of OpenPGP.

You're probably much closer to the people responsible for the OpenPGP standard.
Are there any efforts to introduce SHA512-BASE64 fingerprints? (or at least SHA256)