I would give the Meltagun squad Champion a combi-Melta so they can have two shots at least once. One Melta shot isn't very likely to take out a vehicle, you want two or three to make sure. Also I would swap their Bolters for CCWs seeing as they're going to be getting up close and probably stuck in with Malek, and you aren't going to be using the Bolters much anyway because they'll be targeting vehicles with their Melta. I would say make them 10-man for the second Meltagun and put Malek with a Plasma squad, but I understand they won't want to be as close as they would need to be to get him into combat, and you would be wasting the Plasmagun a bit if you did. I think the best Chaos Marine loadout for Huron to join is probably flamer. That way the lack of two special weapons doesn't matter too much, he can contribute with his Heavy Flamer and they're a close-up squad which will be getting into close combat.