It (this modular P320 design) is a neat idea. But I have seen at least one P320 that could not hold a group at 5 yards. The receiver group, slide, and barrel would ‘rock’ in the plastic frame on firing (unlike a conventional design where the receiver and frame are one), thus a different alignment every shot. Others seemed fine, but seems like a design issue to me. When they actually get through all the recalls and any ‘new’ issues, I might get one.
John Garand brought a rifle to Aberdeen proving grounds to compete against the Petterson rifle. The Army likes the Garand but told him nice gun but wrong caliber it was chambered in 270. He was informed a war was coming and all the ammo world wide was 30-06. He went back to Springfield Armory and returned with a rifle chambered fo 30 cal. It was modular. The garand trigger group built at Winchester works in one from Springfield rifles etc. I have one but it’s not my SHTF rifle or the one I would carry into battle today. I have better fits for current combat conditions. The great thing about the garand rifle was it’s ability to work in a lot of environments reliably. But taking a trigger group from one weapon to another has some advantages in the field.