I figured out the other half of the cycling for the AGA 68 idea. Got the idea after finding a cocker slider trigger in the shop. The breechblock is under slight spring tension to help gravity pull it back down. When the hammer is cocked, a lever lifts the block up, like in a revolver, and as it reaches the firing position the wall of the elevator pushes a sliding, springloaded rod with an angled face back into the grip/body, when it reaches the locking notch in the bottom of the elevator the spring pushes it back forward, locking the breech/elevator assembly into place. The slider trigger is pulled, releases the hammer, and then a slight bit of over travel after firing slides the locking rod back and allows the elevator to be pulled back down to the feedtube.
I really wish I had access to a mill right now lol.