VirtIO-IOMMU

So in the future it will be available as an (advanced) option [did not read the diff/changes in code]?.
if the patches get accepted, then yes, it would be an advanced option of the machine type

P.S. I assume that IOMMU part in GRUB2 kernel configuration will also be added (for Intel: intel_iommu=on and eventually: iommu=pt) ?
no, this has nothing to do with the patches at all, since for using viommu you don't have to use real devices, you could also only passthrough virtual nics/disks/etc.

though i am planning on making it easier to activate/edit such things on the gui in the future, but no timeframe for that yet...