I did a little more research and it looks like that these U.S. jellies lack protein so aren't quite like the beetle jellies from Japan and would not be meal replacements for these beetles (especially adult female stag beetles) but rather are supplements. Other pets may not need the added protein.

Rus shared a recipe for DIY jellies. I wonder if we can modify it by adding our own protein sources and whatnot. There might be some potential as a staple, consolidating water sources and food into one, further simplified solution. I'd be down to experiment; a dubia version would have carrots and grains, a lucanid version would have protein, etc. I'll have to research what kind of protein the Japanese jellies use, and I'll have to test how long DIY jellies can last in a busy colony without molding.