When you write that awesome prototype, your management will be thinking about rewarding you, not blaming you. They will listen to your concerns.
So, you can say that it's not ready. You can mention that you alone are not enough to fix the bugs that come up in greenfield code right away. You can even ask for people to help on your project. Why would management say no if they want to sell it?
Then when a manageable amount of bugs come down the road and everybody is happy, you are now in a far better position to negotiate a higher salary. You have far more responsibility. You have a great track record. Nobody wants you to leave.
The cost of developing a prototype when you handle every error you see along the way, set up all of those dev tools (tests, logs, CI, formatting, etc.), and test every branch like a madman is too high. You'll probably end up taking weeks to develop something that you could "code in a weekend". Then, since you never verified, it may turn out that nobody wants to use the prototype for obvious reasons