Held items-idea to add a bit of variety

Was thinking about the held items like you can give to pokemon in the original games. Could be a good thing for this game. But at the same time could obviously break the game big time. If done right could make the game a bit more interesting. Items for example that when held lowers the hp or defense stat to increase the attack stat and vice versa. Items that add bleed damage to a charged attack. Or passive items that if your buddy is holding increases the chance to get a specific item at a pokestop or that attracts more wild pokemon of a certain type. I dont know. Would need to be pretty well thought out though could seriously break the game at same time. But could also work to give different uses to certain pokemon for example turning a tank type pokemon into a bit more of an attacker at the cost of survivability obviously. Then how would you get these items? From wild pokemon? Bought with coins? Badge rewards? Mini games/challenges you can do at home when you're not out and about? I dont know. Would add a bit more depth to the game if was implemented well. Thoughts?