I should probably check that in a lab and look closer at the Backup Copy feature but perhaps the community can help me understand this one

Scenario:
Backup Copy is used to move the daily backup to an offsite repository via a tiny WAN connection. The first full backup will be manually moved with a USB disk to the target repository so that it can be used for seeding/mapping.
The WAN connection will be too slow to ever successfully copy a full backup offsite and the primary backup job will create full backups from time to time, so the backup chain will also be recreated.
So, will it be possible to do a forever incremental Backup Copy job without the need to copy over a full backup ever again?
And if so, where are the limitations or risks which could force the copy of a full backup?