The problem is that true innovation requires freedom to innovate, and that's expensive because it could mean a new caliber, new logistics, new training. What's the realistic distance that a handgun is used in combat? Let the military define performance only--penetration through barriers or body armor, amount of energy on target at a certain distance (without specifying number of projectiles), number of targets to be engaged with a loaded weapon, weight of that loaded weapon, dust/grit tests, corrosion tests, etc. but not specify a caliber. Then let the manufacturers big and small slug it out, with a royalty to the winning design but a separate process to award the production contract for the weapon and ammunition.
I can easily imagine, for example, a small-caliber machine pistol using maybe a 5mm straight aluminum case, performance comparable to the FN 5.7mm but full velocity out of a short barrel with long, thin bullets that tumble for maximum damage with ball ammo. 30 rounds in the gun like the Kel-Tec .22 mag pistol, optional burst fire at something like 1200 rpm, say three rounds a pop, and a fiber optic/tritium day/night holographic sight. That might actually make a real difference in terms of hit probability--only the rounds on target really matter. Perhaps the old Mauser C96 forward magazine form factor would make a comeback. Han Solo would be proud!