There is an open source Loop Auditioneer software for auto-finding loop points: http://loopauditioneer.sourceforge.net/
As its source is open, maybe it could be used to implement auto loop finding feature in Grace?
Thanks for the link Zyguli. It's a good thought. LoopAuditioneer's license (GNU/GPL) would forbid re-using source code in Grace (AFAIK). Alternatively, a high level explanation of loop finding techniques would be useful as well, if you know of any.
PS: Grace was open sourced some time ago also. https://github.com/s-oram/Grace