The weapon and the player are two different things. We are working on the interaction, but changing only one of them won't magically change the other.
The thing is, the game doesn't calculate object sizes openly much. I'm saying you might have to work with box variables and stuff in the code to interpret a weight, then adjust player speed to match a value. Problem with this is people don't code most weapons right. It'd be incredibly difficult to make this function with all weapons. You'd have to set each weapon with it.