From my perspective, you should be ok with the described scenario, though, you can schedule weekly synthetic full, and perform active full only once a month ( that’s what a variety of our customers are doing). You can also setup DPM actions as the post job activity, so that, once the Sunday active full has finished, DPM will copy weekly-worth backup chain to tape devices.
As to the size of backup data, extreme compression is likely to help you here.
Additionally, I would still recommend not turning a blind eye to Veeam tape functionality, especially, when we are talking here about copying to tape backup files that are produced by Veeam Backup and Replication. As you might imagine, we, in contrast, to DPM provide you with vast options of how Veeam backup data can be tracked, on which tape media do particular VMs reside on, what medias are required in order to restore certain VM, how copying/restore process should be handled, etc.