we have kind of the same issue, for us its files which have been overwritten by newer code outside of any repositories...
Anyway, what we do is simply backup the Vm's with Veeam and keep them on deduped Windows volumes residing on big "cheap" JBODs.
We have one Fileserver which is around 2TB and still have all fulls / incrementals of 2 backups per day since 2010 when we started with Veeam:)
Since it's all the same VM (and thus same files) it's actually pretty good dedupable with windows. The maximum Volume size is around 62TB, after that you need to switch to a new volume.
As example one of our Fileservers takes up 31TB on Disk but actually these are 168TB's of backup files, so nearly indefinite backup files are possible like this.