Hi,
Well, as you pointed out OSSV can't do BMR, so if you want that functionality, you have to consider a 3rd party product.
Syncsort is an interesting choice, indeed, but it effectively replaces OSSV agents with their own ones, capable of 'talking' to the SnapVault target on the NetApp filer.
The other option could be e.g. Backup Exec System Recovery, which does what it says on the tin and requires any secondary disk space to function, but is not integrated in any form or shape with SnapVault.
Regards,
Radek