Sounds good. I'd think the wide lens would be the best hold item for the garchomp, yes? to up the accuracy of his moves. as for a weather summoner, do you have any suggestions? As you can see I have two maybe three empty slots on my team. I feel giving garchomp sandstorm might immediately boost his ability but it'd waste his immense power and speed on a turn, which could cost him some serious hp.
Oh, of course; my suggestion would be Hippowdon. Now, since both Garchomp and Hippowdon are weak against ice, this combination would make you particularly vulnerable to them, but thankfully, latter's got enough health and bulk to withstand their attacks, so it shouldn't be any trouble for you! Plus, it's got access to Slack Off, if I'm not mistaken, and with that, you'd be able to recover itself at any time.