ElectricDragon
Explorer
It all depends on the campaign. A one-shot is a simple campaign. Sometimes it is necessary to limit choices: one of my campaigns centered around a magic university in the middle of the wilderness. Every player must be a specialist mage, no two could be the same specialist type. Only basic races (human, elf, gnome, dwarf, Halfling, half-orcs, half-elves). To graduate to 1st level required each mage to make up his own personal spell (DM approved) that no one else would have. Further levels gained required also a new spell made. 7 mages. Good thing the "wilderness" was really tame and easy. Even those who thought they could not make up a decent spell, made and used (at least once) their spell successfully, in combat mostly. Only lost one mage, nice campaign. I believe everyone enjoyed it. But no one wanted to play the mage in the next campaign, lol.