The World's Largest Dungeon
A wizard is also a good choice for arcane support becasue their spellbooks offer them a variety of spells to choose from to memorize and can accumulate as many as they can fit into their spellbooks. The downside is that the party is going into a dungeon and once deep inside as the higher level spells are technically becoming available the ability to find new spells on scrolls or in spellbooks will be quite restricted (outside the normal selection of two new spells the mage has puzzled out on their own every time they level per the rules). This combined with the wizard’s typically (though not guaranteed) poor combat abilities makes this a class to hesitate on choosing until all possible scenarios have been thought through.
Any wizard PC may start play with a familiar per the rules. If the player decides to wait to call for a more powerful familiar at later levels they risk not getting it due to being in the dungeon.