You don't need the Restoration VM to have the same resources as the real one. It only needs enough RAM to run Linux. 512Kb is usually enough. You can even get away with less, potentially.
However, if you want to mount the backup on the Node, here are my notes about how to do so using NBD:
Extract .vma from .lzo backup:
# lzo -x backupname
Now extract .raw from .vma and save it in targetdir
# vma extract filename.vma targetdir
[The downside of this is that you now have the original backup, the non-compressed backup, and the .raw. Three versions of the same file! This takes up disk space!]
Now we want to mount it with the help of nbd
# modprobe nbd max_part=63
[We don't really need 63 partitions but that's what always seems to be used]
# qemu-nbd -f raw -c /dev/nbd0 restored.raw
# mkdir /mnt/img
If not using LVM:
# mount /dev/nbd0p1 /mnt/image
[Where p1 means partition 1. If you need partition 2 you would use p2 etc etc]
If using LVM, before mounting you will want to run vgscan to find the VG, then vgchange -ay vgname to activate it, and then mount it as /dev/vgname/root (or whatever) rather than as /dev/nbd0p1]
Now you can work with the mounted image on the Node so you can copy your files and directories.
When you are finished:
# umount /mnt/image (or whatever you mounted it)
if using LVM: vgchange -an vgname
# qmenu-ndb -d /dev/nbd0
# rmmod nbd
[if necessary, killall qemu-nbd ]
And finally delete the extracted .raw and .vma.
NOTE: Someone commented to me that you can directly mount a .vma. I did not do so and don't know what additional steps are required, if any. Maybe I misunderstood. Or naybe someone can tell us.
Also I have not tested the above with LVM. See
https://projects.letic.fr/projects/public/wiki/Proxmox_KVM_Restore_files