I'm currently testing a new modpack, and I keep seeing Spawner Agitators in the chests i'm looking in. As this is meant to be an expensive item due to the ghast tear and the steel, I would love a config option to remove this from the loot tables.

Agreed with the 10% of the current chance :)

Oops, meant Compressed Iron not Steel - looks much the same.

Yeah the default weighting is a bit common. Discussing with @MineMaarten about this, my gut feeling is to leave it in the loot table, but make it much rarer (say 10% as likely).