SAP SD pricing in S/4HANA — standard condition types or keep custom routines from ECC?

We are migrating a client from ECC 6.0 with heavily customized pricing procedures to S/4HANA. The standard condition types cover most scenarios but about 20% of their pricing logic relies on custom tables and routines. For those who have handled this transition — did you refactor into standard condition types or keep the custom pricing in S/4HANA? Any gotchas?