We discussed this on irc. I like the idea of providing csv import/export functionality and Fabio is filing a ticket for it. This would be a nice project for one of the new people hacking on stem, though I'm happy to do it if someone has a pressing need for it.
I'm less interested in xml though if someone wants to do it then patches are welcome. Json is already covered by Onionoo (we plan to make a python Onionoo implementation later, but it may be a while).
Gotcha to be aware of is that Stem currently just parses relay/bridge server and extra-info descriptors. Consensus entries will be easy and tops my todo list for descriptor work, though I've been busy helping volunteers of late.
Cheers! -Damian