I think your first idea sounds good tbh, its a permanent fixture to that operative from then on. Since most rare equipment is basically a weapon mod then it makes sense that it just permanently becomes part of their weapon.
I think your second idea sounds quite broken and unbalanced, which in the context of it being a single/coop experience, it could be quite hilarious and I wouldn't say no to it.
Ah! Okay. So what I'm thinking is that you don't pay for it. Earning it is already enough of a payment.
Personally, it's a piece of equipment so I think it is just added to the stash and chosen before battle like normal, except for that Rare equipment is free and won't take up a selection choice for your equipment at the beginning of a game.
In games like Necromunda, the fighters get attached to their stuff, but I think in KT it makes sense that operatives would be willing to share based on the needs of the mission ahead.
So, it's added to the stash like normal, but when you select it, you give it to an operative for that battle only. Then it goes back in the stash. This is a formality though, if you do just want the same guy to have it the entire campaign then you'd just leave it where it is on that guy. That make sense?
