Do I hear my name?
If you're running anything after the 1st patch (the "final" patch was the 3rd), pickpocket has been
completely nerfed. Completely worthless skill. Don't make any party plans based on pickpocket.
Don't know if you're looking to min/max, so that will change any advice significantly. The good news is that Wiz8 is so well done that *any* party can be made to work. Some will be very difficult, but there's no party that's hopeless. I'll give you some ideas on a party that's pretty optimized, but you can vary it however you choose. Overall, I emphasize melee rather than hocus-pocus, so that will color my recommendations. There's nothing that says you have to be a Disciple of the Pointy Stick, so again you can consider my bias as you review my thoughts.
1) If this is your first run to completion, you want a ranger for autosearch. There's just no substitute. Humans and mooks are decent choices. Although you'll want to emphasize bows, rangers actually do quite nicely in melee with polearms if they're developed for it. With your proposed party, I'd drop the alchy to make room for the ranger. You'll be a little weak on casting overall, but it won't be a crisis.
2) I love Wiz8 monks and humans are a good race for it because they get good stamina. When you get to the later parts of the game, your monk will be getting numerous attacks per round and battles will last dozens of rounds. You'll need stamina for every one of those whacks.
3) Gadgies can be a lot of fun. They stink in the early game but can be very strong by the end. I'd take human over hobbit, though. Gadgies use stamina to use their items and hobbits tend to be a little weak on stamina. With the party you're proposing, your gadgie is going to be your locks-n-trap guy. Make sure you spend your skill points appropriately.
4) Samurais are generally underwhelming. Their access to the wizardry spellbook makes for some interesting options, but you're not really positioning him to be a caster, even a secondary one. Vanilla fighters might be a bit boring, but they really bring the noise. A lizzie fighter with a certain sword you can get early in the game is a beast early on (and eventually you switch to better swords and keep kicking mucho butt). Up to you.
5) Bishops are hard to develop properly. Certainly, it can be done, but it's not a cakewalk. Yours is positioned to be the party healer. Make sure you emphasize the divine spells. For attacking, you might consider the psionic book since it pairs nicely with the divine book.
6) Alchys largely stink. At high levels, they get some very interesting spells, but getting them to that point is less than entertaining, and your gadgie will actually be able to do most of those interesting spells via gadgets. That said, you want to get somebody in your party built up in their alchemy skill so you can get into potion-mixing-for-profit. I usually use my ranger for that, but you could use an alchemist if you wanted to.
7) Unlike Corwin, I don't mind Valks. The "cheat death" thing isn't all that useful unless you really screw the pooch in a fight, but they bring some real damage with their polearms and (since they don't have many skills they need to spend skill points on) they make excellent secondary healers.
Hope that helps. Feel free to ask more--I just hate to talk about Wiz8.