A test concept for a if a Mega Mewtwo could return to the current a unlimited format. A mix of old and new.
After using Mewtwo Spirit Link to prevent losing a turn, you can use Lost Vacuum on the follow up turn and attach a Hero Cape to give a Mewtwo even more Health. Use Natu to flood energies to Mewtwo and the old Double Colorless doesn't have -20 penalty.
The basic Mewtwo doesn't have the injure itself penalty.