I would have doubts on getting it to work. A vigorous eater would need to be researched carefully otherwise may be too flighty even if of small size. Also I think congrats on a backup plan for the neons as they could get eaten by such a fish but 10 gal would be small for them as well.
I'd be looking at something as a display fish in the 2 to 3 inch range which doesn't need to school.
I have looked at rams or gouramis here but I'm sure you would have more options there.
Personally I'd look into if the size of your school of neons can be increased eg 10 or more and say a trio of small chain loaches.