Hi,
I'm just a user, but the impression I get is that right now there are not
many developers actively working on Trisquel. Those that are seem to be
focusing quite heavily on Trisquel 8, which is being seen as a high priority.
So, I think you will have difficulty finding a Trisquel developer that would
be willing to work on a specific release for Raspberry Pi.
I haven't used Raspberry Pi myself, but I would think the main issues in
getting Trisquel to run would be whether it is compatible with the
Linux-libre kernel and/or the Libreboot firmware.