if you don't mind sending ALL you transactions as RBF... simply add "walletrbf=1" to your bitcoin.conf
Failing that, don't you just add "true" as the fourth parameter to "createrawtransaction"?
createrawtransaction [{"txid":"id","vout":n},...] {"address":amount,"data":"hex",...} ( locktime ) ( replaceable )
...
4. replaceable (boolean, optional, default=false) Marks this transaction as BIP125 replaceable.
Allows this transaction to be replaced by a transaction with higher fees. If provided, it is an error if explicit sequence numbers are incompatible.
so something like:
bitcoin-cli createrawtransaction "[{\"txid\":\"HEX_TRANSACTION_ID\",\"vout\":0}]" "{\"address\":0.01}" "" true