Considering that the US converted cluster munitions into training shells by replacing the bomblets with concrete and a bit of explosives, I wonder if you could use the same shell body to deliver HE, smoke, and all kinds of submunitions (including illumination). If yes, you could just design an extended range, full bore shell with different payloads and optional base bleed or rocket assistance, and just produce the same shell body. With something like >>20713
you don't even need a different shell body for guided projectiles. Not that this would revolutionize artillery, but maybe you could get rid of one bottleneck if you make a big stockpile of shell bodies in advance, and then choose the payload, fuse, and optional ranger extender modules based on what you need and have. After all, a cylindrical steel object should last for a few decades with proper storage, especially if it's not filled with chemicals and whatnot.