I'm both a fly tyer & jig maker, and I use a lot of barbells. I have given a lot of thought to having a mold, or molds made for those eyes. My biggest issue with the lead eyes, is they tend to break easily if you hit anything hard with the fly, and I will fish the flies around bridge pilings, riprap & other hard structures. If that issue could also be solved, then it would be a great mold to have.
I've even thought about making a mold that would take a wire insert, to reinforce the center of the barbells, but not sure how practical that might be.
I've been using a lot more brass eye's the past 10 years, because of that breakage issue with the lead eyes and because they're lighter. I fish in shallow water much of the time and don't need heavy barbells for a lot of the places I'll fish. I still use the lead, but fish them where it's open water, deeper, and not in places that may have things that will break them.
I've mentioned this too in other discussions and most folks say they don't have the breakage problem, so I guess it's how you fish them.
If Do It was to offer them, I would buy the molds, that's for sure, because for me they would be worth having.