When you say "holding" do you mean in the player's inventory? Or in the player's hands?
At least with Fallout 3 we found a global list of all objects. In theory, we could expose functions to walk down just the weapons or ammo in that list, returning each object form. From that point you could modify the base form and weight would adjust accordingly. However, I am not sure that we would ever expose the functions to walk over everything. It seems somewhat dangerous. That was the decision we came to a year or so ago for F3. I would need to talk to Ian about it, and also find the data again before we could do that.
Thank you very much for the response.
I meant holding as in the players inventory...
Though if it were possible to double the weight of weapons and ammo that would be all I need for the mod I am working on and counting how many guns the player has in his inventory would not be necessary at that point.
If it can be possible to do this by modifying a single variable I think that would be ideal especially since it would allow people to add new weapons and ammo they would be fully supported with minimal hassle. I think this would be the cleanest implementation imo.
Though I am not aware of technical limitations or how expensive something like this would be or what kinds of problems it could pose.
Let me know what you decide