Players has no use of empty tube after the usage of M72 LAW and it requires for player to do additional actions to remove empty one-shot launcher from his inventory, so probably it should be automated with rule of cool.
So, my proposal:

1. Player shoots one-shot launcher.
2. As soon as player tries to switch to another weapon, player character drops the empty tube on the ground with cool animation and physics.
3. Empty tube would be a physical object that would persist on a level for a bit as "battlefield garbage" to increase immersion similar to explosion craters, bullet casings, destroyed vehicles, bodies etc.

RHS in A3 already does it - player drops the launches as soon as he switches to another weapon.
https://youtu.be/T8EXHVzV6O8?si=cE0stUVDYaLYnDXm