If the collapse is early, Egypt could take the entire Mediterranean coast. It came close to doing it under Ptolemy III. Ptolemy's armies even operated in Persia, but it's hard to see Egypt holding the east for all that long.
Breakaway Greek kingdoms in Mesopotamia and Media are plausible, in addition to the one in Bactria that succeeded in real life.
There were multiple kingdoms in Asia Minor from early in the Seleucid period, paying mostly lip-service to the Seleucid kings as overlords. From west to east: Bithynia, Pergamon, Galatia, Pontus, Cappadocia. They would become formally independent earlier. With no Rome, however, Macedon could revive and take over much of the area.