I think that I understand your use case, but I'd like to know how the dumps are delivered (scp, rsync, smth else) ? Unfortunately, the current version of VAL is unable to meet your requirement out of the box, so I consider this as a feature request.
Since you've mentioned that you don't have much control over the dumps, I'd like to add one more thing - it is important to ensure that every backup job starts not sooner than the dump file has completely arrived to the host. Otherwise, you may end up with one half of dump being in one backup file, and the other half of dump being in the other. If you already perform such check, please tell us how you do it. You could accomplish that by using custom crontab script that would perfrom the check and trigger a job to start, that is, you should not use Veeam scheduling wizard. Another option would be to use a pre-freeze script
that would perform the same check before taking a snapshot.