I attended a developer presentation at FS Punta Mita when I was staying in the hotel there last year. The salesperson said that so far, all the FS residence clubs trade with each other on a 1 for 1 basis. It sounded like you could book remaining inventory in other clubs when the owners there hadn't already booked it during their exclusive booking period. She made it sound like that wouldn't be an issue, but it WAS a salesperson, so YMMV.
Also, the "pure" residence clubs trade on a more than 1:1 basis into the FS Aviara and Scottsdale. I believe the ratio was 3:1. For example, one week in a 2 bed in Punta Mita would trade for 3 weeks in Aviara. It sounded like this was quite do-able, as apparently they have a waiting list of owners trying to trade out of the "timeshare" properties into the "residence" properties, so they hold a lottery every year to determine who can trade into the "residence" properties.
The summary of all that is that "residence--->timeshare" is easy
and that "timeshare--->residence" is hard.
I will close by noting that all of this came from a salesperson, so it could be their "interpretation" of the truth, but I thought I'd share it anyway, since information on the FS program is pretty hard to find.
Best regards,
Michael