1. Tell the player he should ally with AS to trigger the chain. Somewhere within the first message that he gets from AS there should be a line for it. Otherwise the chain won't trigger for him when he kills the wandering rebels in Bithynia and he won't know why.
2. The first "helper" stack of AS should be spawned as a Pergamon army. Seleucid AI won't help Pergamon conquer Bithynia, it just walks that army home instead.
3. Don't spawn extra garrison in Bithynia for AI Pergamon and start Pergamon AI allied to AS?
4. It'd be nice if AS sent some gold at the end of the war, Pergamon will be bankrupt from the whole thing. A couple thousand shouldn't break AS.

All this to prevent the player from jumping at Sardis on turn 2, which seems way more favourable than the whole Bithynian adventure.