While I've considered cross-slot-type interactions (currently the only items vaguely of that nature are slot Shielding-type utilities), they can make the UI a bit harder for the player to understand. I have a few more ideas in that vein, but they always get put off due to logistical and usability concerns, and this would fall under that category.
The specific benefit/feature you mention would lead to other problems as well, including making it too easy to hit the 26-slot limit, which is already achievable by the end of the game
. Once a player has near/at the maximum number of slots, the item(s) in question would no longer work...
I think a better way to create a wider variety of strategic options is to focus on effects that improve the effectiveness of other parts, more of which you'll be seeing in Alpha 11 next week with the addition of weapon cyclers, actuators, and capacitors. Lots of new items coming!