I have just completed your mod and it works very well. I find that the spring under that orange thing in the plunger works better though. thank you for your wisdom.
There are some problems I can foresee. Will there be a turret for firing? How do you plan to move the said turret? How fast will you be able to move? How will you compensate for the few inches you need for running? How do you plan to see inside a cardboard box? Will you be able to fire while moving?