Ghasts do spawn now, but they make no sound or expression when shooting fireballs.
Fire balls are invisible and still break blocks. I recomment prop damage to be disabled for fireballs or make ghasts not attack at all, or even remove them again if none of this is doable.
Now to the costum drops:
Id say zombie pigmen sould drop gold tools in a rare case and have their cooked pork droprate reduced, since they are rotten zombies and most of them should not be edible at all.
Also, if ghasts will stay on the server, they should drop something rare and valueable, since they tend to fly above unreachable ground or lava. Id say lets have them drop fire blocks in a medium rare case, so we can craft chainmails again.