My hope is that combat spells work kind of like maneuvers in Tome of Battle. Level only describes when you gain access to them. Slots are held in a general pool without level distinctions, and the effects of the spells scales in many ways.
I prefer the idea of magic as an expression of the caster's arcane power, rather than a formulaic recitation of a spell which creates a specific effect with a specific strength. Think of it as the "I kill you with my mind!" school versus the "magical bullet" school. The "I kill you with my mind!" school of magic design has effects who's power is entirely dependent on the caster. The "magical bullet" school has magical effects which are dependent only on themselves, regardless of whether they're being used by an archmage or an apprentice. Think of a crossbow as an example of this style.
Right now we're balanced between the two visions. Caster level scales, but usually has a cap, and DC does not scale. This is necessary because spells have levels. If everything scaled, a level 3 fireball could be the equal of a level 6 evocation spell, which would reduce the purpose to having slots for specific spell levels in the first place.
But if there are no level specific slots, and spells are just held in common, it makes sense to open up scaling completely. So what if a fireball you learned at level 5 has grown to equal a spell you learned at level 25? It cost the same resources to cast.