The only way I would be ok with build switching without visiting an NPC would be:
- Set Player Health 1
- Set Player Max Regeneration 0, duration 60 seconds.
- Set Player Max Endurance 0, duration 60 seconds.
- Set all powers state to Initial Recharge.
- Wipe all Buffs/Debuff on character.
In other words, we do NOT want players to be able to situationally change power selections.