Maybe I could use the HP DL 385 G5 I have with the MSA 70 and run something like FreeNAS on it for another datastore option?
That's one option. Something that would be good for, to be honest, would be your StorageCraft server, if you go with that.
I was thinking use it as a NFS datastore and a place to store the VM files for my current physical machines like was mentioned above. That saves money on a secondary backup solution.
Actually, that would be a tertiary backup solution, as you have Veeam and BE already. The original decision seemed to be "buy hardware or buy another backup solution". It seems that utilizing current hardware like that could avoid both?
I'd get rid of BackupExec with the P2V of the physical boxes and be able to use Veeam. That eliminates cost of software. But, I cannot avoid some investment in increasing backup storage. So this does not completely eliminate a need for more hardware but does decrease the cost of the hardware needed by a large factor.