Can you use traditional cipher be used in public key cryptography?

I wanted to run a brainstorm to the community.

To have public key cryptography you need a one-way-function.

But what if you made a public key based on a known cryptography scheme?

For instance Gematria can be used to encrypt a message. What if Gematria was used to create a private key. And a public key was created by “many cycles” (iterations) of the private key.

The secret message (plain text) is then encoded by Gematria according to the private key.

Then knowledge of the private and public key decipher the message.

Is it possible or too easy to crack? It is dependent on the deciphering, but I think I have a simple enough scheme to work.