Not too fond of the fact that there is an "encounter" power variant though. Im not a fan of "encounter centric" design, and 5e is moving toward "adventure centric", so Im not sure about the inclusion of an encounter variant.
I say go with a "recharge" mechanic and you can develop the equivalent of an encounter with more versatility in how you get it back. As long as the recharging action is something you couldn't feasibly do in the midst of a combat (say, taking a minute to meditate and regather the necessary magical energy, rebuild a fetish/focus, inscribe a magic circle and recite a chant to a power associated with the spell, etc.), it becomes an encounter-based spell without the encounter dirty word.
Having one spell that could prepared three ways - at-will, rechargable/encounter or daily would be a neat twist. Of course, not all spells might qualify for each type (I have a really hard time envisioning
sleep as an at-will without significant enough changes to name it something else). And it might be possible at higher levels that what was once an encounter or daily move to be usable more often (Say A 3rd spell level
fireball going from Daily at 5th character level to Recharge at 16th character level)
Example:
Magic Missile
Evocation * Force
Level: Arcane 1
Range: 100 feet
Target: One Creature
You hurl a bolt of force at a target that deals 1d4+1 damage
At-Will: Attack vs. AC
Encounter: automatic hit; Recharge: 1 minute (Meditation)
Daily: 4 missiles, automatic hit
Knock
Alteration
Level: Arcane 1
Range: Touch
Target: One locked object
You unlock the target object
At-Will: Int vs. Lock DC
Encounter: Int with Advantage vs. Lock DC; Recharge: 10 minutes (Meditation)
Daily: Int + 10 vs. Lock DC