Another possibility - if the ad-lib section is fairly short - create the ad-lib section in one of the Composer Intros and use that instead of the built-in style Intro. This assumes that you don't want to use the other Intro in the sequence. You would of course have to copy the intended built-in style to the Composer and then over-write one of the Intros.
There is another possibility if the ad-lib section is too long to fit within the 16 measures available in the Composer Intro. The entire ad-lib section could be recorded as a separate sequence - say in Song 2 of the sequencer. Then, the 'normal' sequence could be recorded in Song 1 of the sequencer - including an Intro if desired. Having recorded the two songs, it may be possible to 'join' them, using the editing facilities in the KN7000. I haven't tried this but will experiment when I have a bit more time available.

......NOT a simple process but it may work

For Ted's purpose, I would think that my initial suggestion would fit the bill, despite the asynchronous nature of the style to the sequence measures.