Would it be possible to have the gather rate only apply in claimed map grids ?

does the notrespass option suitable for you? 
/lordadmin notrespass enable|disable - Get gather bonus only in not captured cells or cells you own. Enabled by default

No, I mean to have the gather bonus ONLY apply to owned cells, and NOT unowned ones.
This would encourage more players to claim cells as they would NOT get the bonus unless they own the land.

We are also having a few issues with gather bonus not working on clan mates, and only leaders being able to put down banners, but I need to test a bit more before reporting. :o)

ok, make sense. I will add it to the next version