Implement a way to import Virtual GPS lists directly from Project-GC. This would be very similar to importing Bookmark lists from Geocaching.com.
Three things required:
1) Under settings somewhere, a field to add a Project-GC access token.
2) Using an API method to retrieve all Virtual GPS lists (id, name) the user has.
3) Be able to fetch all cacheIds or Gccodes from a specific Virtual GPS id.
I haven't tested the "Import bookmark list", but I assume it fetches the cache data itself after it has the list of geocaches. It would have to be the same way here since Project-GC ain't allowed to send the cache details to another partner.
Customer support service by UserEcho