Harvesting in WvWvW should be linked to supplies at camps or keeps.
One suggestion would be that players could deposit resources gathered in borderlands/battleground at a supply camp.
For example wood at lumber will. Once enough wood has been gathered and processed at the mill, the dolyak will take off on a supply run.
Npcs near camps would also go out to gather to make sure that a minimum amount of supplies/dolyaks are generated.