Would it be doable? What classes for the 5 PC characters do you recommend.

I don't see why not, and probably the same classes one would use with other races.

Too be honest, a single race party isn't going to be significantly different from a mixed race party, as the effect of race on a character's abilities is rather minor in this game.

On the other hand, a single *class* party could get interesting. I haven't played the game (other than the tutorial and doing some tests), but I suspect that the easiest class for this might be Cleric. (I suspect that you *might* need the Use Magic Device on some characters, but fortunately the game lets you level up cross-class skills.) Good luck trying this with classes like Rogue (good luck dealing with undead and other sneak-attack immune enemies), Bard (probably the weakest class overall), or Sorcerer or Wizard (either class is extremely vulnerable, though at least you can have fun playing with all the spells the game offers).

(Of note, some people have done single class challenges in other games (Final Fantasy Tactics being an example).)

One more thing I should point out: A single race party is probably suitable for a first time player. A single class party is *not*.

The game would be a little slower because of the gnome strength penalty but this shouldn't be a problem.

A party consisting of Cleric, Druid, Sorcerer or specialist Wizard (divination and abjuration as forbidden schools), Bard and Barbarian (max strength) should work well for example.

If you think bard is weak, you aren't playing them correctly. Especially in a game where every step of the way you encounter enemies that are susceptible to charm person or dominatation. I have soloed the game as a bard, and it is actually not that hard to do so.

Check out the How to Bard thread here.

All-gnomes party is doable, but why? Their limited speed makes game a bit slow, and with higher resolutions it may be hard to see them at all :) Also, I would use max 4 chars (preferably 3, at least one rogue and bard or sorcerer) for faster leveling - if you enabled max level 20 or higher, that is (best playing with Co8+Temple+, almost essential).