I would like to have only purple lums for now.
Implementing lockjaw and power cans in general is separate issue in development that I would need to overcome somehow. One thing at a time.
Also I would like to refine the usage aspects of superpower cans - you could use them anywhere, as long as you have powder left, and disable power ups at will.
Cans powder you could buy for points at Teensies Stores, find in the hub worlds and levels in chests and gain via killing the enemies.
But if anything, I would opt for having both purple lums and the metal rings that you could swing on only when having blue power can activated.