The Dragon (or any number of other "I'm a monster who casts Cleric spells as Arcane!" creatures) could take "Scribe Scroll" and actually scribe a scroll of "Arcane Cleric Spell". Cheeky, but true. Heck, a 12th level Warlock can seriously go to town and do all sorts of stupid shit.
The damage caps were introduced in 2Ed, because people also (sort of) had HP caps. It was to keep things balanced (as in 1st Edition, there was a HP cap but not a damage cap - direct damage was brutal). The problem is that in 3Ed, people have a lot of HP. Suddenly, the damage caps don't make sense. But seeing as the save DCs suck for spells that aren't your highest 2 levels, it hardly matters. Or maybe I'm just bitter about my first foray as a fireball Sorceress against DM "Everyone's a Rogue! Evasion! HA!"
There's a really funny Prestige Class somewhere, a caster one that gains special abilities that unlock spell abilities from 1st and 2nd Edition. "Seeker of the Lost Mysteries" or something like that. They lose the damage caps to spells, their lightning bolts bounce off walls, and fireballs spread to fill the area.