How would one hold that in place? Just drop it in before putting the cell in? That would probably work for cells in parallel, but what about cells in series.
One is obviously using that in a tube and the dimensions need to be close--the diameter of the disc and the diameter of the tube.
Another issue is how tall is that rivet and can you smash it down any, since it's brass?
Third, we're not just talking about the forward battery making contact with the pill, but the two batteries making contact with each other, which could be equally problematic.
If you have to use two of these spacers, say one for the forward battery>pill and one for the two cells in series, then you have two of those in there and you better have some wiggle room.
You'd have to carefully drop it down against the pill/driver, drop the cell in, then add a second one if needed.
Still, probably not a bad idea.
I made a crude one for my ShiningBeam I-Mini, with reverse polarity, to use with my naked Sanyo UR14500Ps, but went back to the button top 16340s.
Chris