Probably makes no sense at those ion energies.. no mean-free path in air..

Next is how much current can be carried?

I was fantazising on 3D-printing. Now there is laser melting (or arc melting) of powders. What if a beam of material is available?

any way a clean atmosphere will be needed to prevent chemistry, so we may go back to vacuum, and then it is nothing else than some kind of PVD.

Well some very high-speed local PVD still has its charm.

So mass carrying capacity of a plasma is the key. A neutralized focused ion-beam with A/mm^2.  No electron torch but metal-torch.. I believe electrostatics won't help.

just for fun..