Is there any API I could hook into to make AsieLib more compatible with EiraIRC? (That is, a way to relay ingame messages to it after they go through my tweaks?)

I've started preparing an API a while ago but haven't gotten deep into it yet.

How would you suggest this to be done? Some 'RelayChat' event you post to the EventBus for EiraIRC to handle? If that sounds about correct, I could add it for the next release.

Sounds about right, as I only want to relay certain messages (when chat-radius is enabled, for instance, I will make it so only shout messages and messages sent close to the spawnpoint get sent).

I've implemented this API-event in 66a3968.
Post an instance of this event to the Forge EventBus and EiraIRC will do it's job.

You might also want to make sure your ServerChatEvent handler is prioritized higher than mine (mine is at default value), so they always go through yours first.

Let me know if you need anything else from my side.
I will be shipping EiraIRC with that new API with the next release (coming probably this week).