Your wording is a little confusing. First, it should read 'rewind your opponent's creature.'
Next: the cost ratio for rewinds is (2 + 4x)/R, x being number of times you use the skill and R being total number of rewinds. The spell's cost ratio is 2x/R
In theory, as the cost outweighs the actual spell, this should be more balanced. However, RT is already considered powerful. It's only not OP because you can't easily spam it- Eternity is rather hard to spam with its playing cost. With this, you're making a creature that can spam RT at an extremely cheap cost.
You neglect mitosis and SoR. I'm not even talking about the combo, just separately mitosis or SoR. Either one could allow you to instantly shut down your opponent, provided that your opponent uses creatures.