Split backup of 1 domain

I love virtualmin. Thanks a lot for saving my ass with this product ^^
I am preparing to open a wordpress multisite network with lots of sub-sites in it. Basically its 1 domain with lots alias domain on it.

My problem is:
This network will be huge but its 1 domain in virtualmin so its 1 backup. But somehow i want to split file backup. Excluded Directories is good for it. I can exclude those directories. Problem in there: how can i backup those directories then? Somehow i need to backup those files like a domain in virtualmin:

Is it possible?

You could use Webmin’s File System Backup module for that, though there’s some restrictions there in terms of incremental backups.