This would work well with Fork-and-merge and I think it more or less exists in Fusion.
Basically it'd be a way to have two or more linked designs with constraints between them so different people on the team (or one person wearing different hats) could make changes to different aspects of the design and have everything updated across the board.
In the example of the Nerf gun, you could have one aspect being the overall geometry, another being the firing mechanism, and another the ammunition holder. If our designer wants to add a wave to the grip, while an engineer refines the firing mechanism, they could both work at the same time and constraints would keep everything from falling apart or allow someone re-merging the two to manually resolve any conflicts.
