I know of 3 races Thomas said he'd put in sooner or later. Where did you get the classes from, though? Anyway, Thief and Assassin would do for "criminal" classes anyway, Pirate would be redundant. As for Summoner... as long as you don't gain some exp from pet kills, summoning will still fall in disuse. Besides, Necromancers summon stuff already.
Wasn't here going to be a ratling race new to ADOM... or is that Jade?
Anyway, I don't know how an Alchemist would work, unless there was a more advanced form of alchemy for them, but how would they fight? not as fighters or spellcasters, and they wouldn't have the other abilities that assassins and thief have, so what? Agreed, summoners would be redundantly similar to Necromancers. What about scholar though? they would be ok fighters and ok spellcasters with the added ability of automatically having all books and scrolls identified. Maybe Potions to. And immune to IBM and scrolls of amnesia. Give them writing sets with a bonus. At level increments give them an area of study, adding skills like Herbalism, Law, Alchemy, Pick Locks, Detect Item status, Music, Metallurgy, Mining, Gemology or others. also give them the studied enemy ability (like preferred enemy ability of D&D ranger class). Have it be random, chosen or be based on the most killed unit so far in the game. Obviously high int and skill levels. Make them good book casters, but bad spell casters otherwise. Maybe wand abilities to?
The obvious difference is that it would be much easier to have lawful summoners than lawful necromancers. In addition, your servants would not be limited to undead, and hence you wouldn't have the limitation of all your servants being weak to fire. As far as game mechanics go, I see a way that a summoner class would work really well without seeming too similar to wizards or necromancers. Instead of basing summons off of spells or a skill like Necromancy, Summoners would revolve completely around class powers. I imagine it could be something like this:
Lv6: You can summon a random monster to be your ally.
Lv12: All monsters you summon are guaranteed to be at least Neutral, A few(~10%) will be companions.
Lv18: You can expunge any summoned creature and send them back to where they came.
Lv25: You can bind a monster of the same alignment as your ally, and summon them later.
Lv32: More(~35%) of the monsters you summon will be companions.
Lv40: You can summon an ally related to your alignment(Solar/Spectre/Greater Daemon)
Lv50: A lot(~60%) of the monsters you summon will be companions.
The Lv12, 25, and 40 traits are referencing things such as Wands of Monster Creation, Summon Monster Spell, etc. The powers that summon an ally are special: These are not normal companions. An allies' level is within several levels of your own when summoned, and you gain a percentage of experience(around 70%) of their kills. You cannot summon more then one ally at a time.