So here is the direction I am initially looking to address this issue...

I created a new "DdlTransactionIsolator" contract, which in part, represents the before/after transactional behavior specific to each "transactional environment" (TransactionCoordinatorBuilder):

public interface DdlTransactionIsolator {
	JdbcContext getJdbcContext();

	void prepare();

	Connection getIsolatedConnection();

	void release();
}

And added a new TransactionCoordinatorBuilder#buildDdlTransactionIsolator method.

This allows us to have behavior specific to each of JtaTransactionCoordinatorBuilderImpl and JdbcResourceLocalTransactionCoordinatorBuilderImpl in terms of before and after processing all DDL.

In DdlTransactionIsolatorJtaImpl, e.g., I use that to suspend any current transaction before we start executing DDL and resume it after.

I'll get a PR ready. But I wanted to wait for others to have time to look at this and also to wait to allow Scott some time to reply.