I would imagine that a little bit of custom code might well do it, might actually be something worth contributing back to the moodle core eventually. My guess would be that all that needs to change is to include custom fields into the configuration options for the block and then the same for which database fields are being merge in. It's been a while since I've written any PHP, but there are some excellent guides on how Moodle's blocks are programmed. Alternatively you may find that the Totara developers (or your Totara partner) would be willing to make the tweaks for you.

Regards

Daniel Bond