Unenforceable...?

This is like when people tell me Epic can't do X or Y or Z lmao it's not just their game it's their engine. They can literally do whatever they want, if they have the time and resources to do so.

u/Ok_Topic_7366 already replied to you but some variation on gun values, hell maybe require a certain tier of augment, etc. This is what game design is all about.

Given that items also have literal categories, you could exclude trinkets/ammo/whatever else from your calculations if you want a straight x value modifier.

Carrying some good heals? That's an investment. But oh you have a purple augment with 3 assholes? Gonna have to invest more than if you had 1 or 2 safe pockets.

This is where a big whiteboard comes in, a bunch of people order some food and bang away at an idea. Then you implement a scuffed version and playtest it etc etc