Jim, you're splitting hairs... or maybe you're splitting spherical powder balls in to flat flakes!
Bullseye may be the
original pistol powder of all of them. It's a flake powder. Unique can do anything that's ever had the ability to be flung as a result of burning smokeless powder and it's a flake powder. Unique may be known to some as a shotgun powder... but a whole generation of handloaders have made Unique their "GO TO" pistol powder for decades.
To the subject, I'd keep in mind what you actually gain and what you give up to get that savings. Even with powder perhaps at an all-time high, it still pales in comparison to what I'm spending on bullets. If I just throw out a "known" acceptable ballpark charge weight for .223, 25.0 grains will work. That's 280 loaded rounds in a pound of powder. That's cheaper than bullets unless you're running lead slugs that you cast yourself or you have some slick swaging setup & your squeezing out home-brew jacketed bullets. If you run a different powder, you can lop some of that charge weight off, too. (look at H-4198 for example)
If you're going to run .223 with pistol powders, your velocity is GONE. Your ability to run a gas-op semi-auto is gone also. If these are not dealbreakers, then you're still in business... but be warned, your point of aim is likely to be radically different than with ammo built to 'normal' spec. So now you're either making quite a sight adjustment or you're going to set up a firearm to run this pistol powder-powered ammo exclusively.
If all of that has been considered, then I suppose it -IS- time to try making some of it up. Report back!