A "Stop-loss trade"?? That's really something new from the world of MT

IB API does not require any "bracket" mechanism - it works with raw orders. It is perfectly ok to submit a stop order with or without an existing position (or other orders to open a position).

I understand the roots of Zorro, but find it difficult to believe that it needs to continue to be confined to the Metatrader model. (with the consequence that all further broker integrations need to dance around these self-imposed restrictions).
If an API allows to place a stop or limit order - let the plug-in place it. It is probably simpler to just do it, than simulate internally.

Or implement BrokerStop() and BrokerLimit(), and/or extend the order() function to allow advanced user to implement any of the huge variety of order types offered by IB.

Freedom! Freedom!