Once BTSX becomes BTS, it simply makes no sense to have PTS and AGS anymore. They should simple get a one time compensation in BTS, that slowly becomes available over the next year, and then all future I3 efforts should go towards improving BTS.
DACs that want to experiment with the bitshares toolkit can then snapshot BTS directly, or snapshot the PTS "last snapshot" + AGS.
In the end having several competing chains simply makes little sense for the community. Chains will inevitably compete for value, and that means as a developer you either have to pick a side, or you will constantly be attacked for "helping the competitor too much"/"not giving enough to our BTSZ chain".