is there a way to do this without generating new schemas and instead applying the old SQL schemas to the new WCF-SQL port?

I agree with @Dijkgraaf, you cannot directly reuse the old SQL adapter schemas with the WCF-SQL adapter.

The classic SQL adapter and the WCF-SQL adapter are fundamentally different in how they process and expect message structures. According to the migration guidance provided by BizTalk360, the old schemas must be replaced with new schemas generated using the WCF-SQL adapter tooling.

"The start element with name '' and namespace '' was unexpected. Please ensure that your input XML conforms to the schema for the operation."

The above error message can cause because the XML message you're sending to the WCF-SQL adapter does not match the expected schema structure specifically, it’s missing the correct root element name and namespace.

When using the WCF-SQL adapter, the adapter validates the incoming message against the schema associated with the operation (e.g., a stored procedure). If the root element name or namespace in the XML doesn’t exactly match what the adapter expects, you get this error.

Reference - https://www.biztalk360.com/blog/migrate-old-biztalk-sql-adapter-to-wcf-sql-adapter/