Full resonance Trinity with Archmage. Is it possible?

I've been tinkering around with CoC Comet and have enough spirit to squeeze Trinity into the build.

The problem is that Archmage adds so much extra lightning damage that every spell deals majority lightning damage.

Cold resonance can be easily solved with Embitter, which converts all that added lightning to cold.

I have not been able to crack the fire resonance problem. As far as I can tell, all of the support gems that could reduce or eliminate the added lightning damage only work for attacks.

Fire damage from explode-on-death seems to work, but the 5% chance from Explosive Impact is not enough. My build runs Blackflame Covenant, and oddly enough Gloom Shrine capped my fire resonance instantly so I think BfC seems to allow chaos damage to also count for fire resonance. Unfortunately Palm of the Dreamer is out as the build requires a very high spirit sceptre.

Can any of you think of another way to solve this problem? I need something that can turn off the added lightning from Archmage on a single skill OR something that causes consistent fire/chaos on-death explosions. Another possibility would be some source of triggered/automatic fire (or maybe chaos) damage from hits that isn't a spell. Explode on death is the only example of this that I can think of off the top of my head, but there may be others.