The external modules will need to be converted to audio. For this purpose you could use one temporary stereo track and mix them to there. I think the VSTi's will convert as the ACW launches and processes the song. It'll probably ask if you want to change the MIDI channels assigned to hardware ports to a softsynth if I recall correctly, before proceeding. If you recorded them to audio you can say no to this.
Then when done you can go back to the MIDI from the hardsynths if you want (and erase that temporary audio track).

I rarely have any tracks that are MIDI if I don't already have a tempo map.


I do not work here, but the benefits are still awesome
Make your sound your own!