I'm not sure why this has to be a decision between two autopilots.  

I have no access to the code but it seems to me that it should be a fairly simple matter to, at the point where the aircraft heading is determined, have an if-test check the setting of a switch/option and select either the current setting as determined by the CWS, or the current value reported by the heading variable in the FSX SDK.

A small change to the existing autopilot, not the addition of a different one, which would be way too much trouble.

Dutch