Total cellular control, of myself only. Think a combination of plastic man but with flesh limits. So long as I learn what cells do what I’m able to manipulate them, I don’t want to change my dna but reorganize it into the various building blocks and specialized cells that we’re all capable of. Can you imagine how fun it would be to be able to covert animal biology into yours? Gain iron plated teeth like a beaver, thicken your bones with enamel from your teeth. Control what shape they grow in. Ultimately it’s main limiter would be time, it would follow real world limits of cellular growth and take an about a week to fully form the change.