I had an idea for a wizard variant, subclass, or alternative for D&DN.
The premise is "casting up". Instead of preparing spells at the start of the day, the caster gathers energy by channeling magic through spells -- this allows more powerful spells to be cast. This... channeler... would have at-will 0-level spells. After casting certain spells, the channeler could cast more powerful spells on the following round.
Burning Hands, then Ray of Frost: Magic Missile, Thunderwave, or Featherfall
Detect Magic, then Read Magic: Identify
Thunderwave, then Ray of Frost: Melf's Acid Arrow, Phantasmal Force, or Invisibility
The Channeler would be about setting up chains of spells to create combinations. At higher levels, a channeler would be able to store spells instead of needing to cast them.
I could see very silly abuses (akin to the 4e criticism of punching a housecat to healparty members), but this is a first draft of an idea.