Multiclassing rogue and fighter is very common. One of my favorite 10th level builds is rogue 3/fighter 7. Anyway, yeah he'll get more HP and better weapon and armor proficiencies. You don't even have to keep his armor light, really. It only matters for tumbling in ToEE, since sneaking and other roguey type stuff is pretty non-existent. (Hence my not having more than 3 levels of rogue, and that really just for dialog skills.) Only worry with armor is the hit you'll take to tumble. But if you've got a high dex, go with the elven chain. You won't find much better than that anyway. Elven chain and a big shield make your rogue/fighter pretty studly.
Wizards shouldn't need HP, if you're using them right. While you can give them a fighter level, it's not wise, because you slow their spell advancement and crafting potential, and that's the only reason they're there. Things to keep in mind, though:
1. Shields have not only penalties but arcane spell failure %'s, so be careful with that.
2. The wooden elven shields, however, do NOT have any spell failure %, nor do they have any armor check penalty. The way shield proficiency works in D&D is you take the armor check penalty to your attack rolls while using a shield if you aren't proficient. Since this shield has no ACP, anybody can use it at no penalty. So your wizard gets a free +2 to AC.
3. Mage armor lasts for hours. +4 to AC pretty much from when you cast it until you need to rest. (Also works for monks!!!!) Only becomes obsolete when you get +5 bracers of armor late in the game.
4. Elves can use longswords and longbows for free, because they're elves. So it's probably best to just make your wizard an elf, when creating him.
Given 1-4, adding a fighter level is just not recommended for a wizard. But if you're dying and can't find a way around it, I guess it's worth a shot. (But you might want to rethink how you're approaching battles... mirror image, greater invisibility, cat's grace, protection from evil, resist energy, etc. can all save your wizzy; as will putting the fighters up front and not letting anything through.
