That might've been doable, but honestly I was pretty dead-set on trying to add new types of jungle grass instead (so once I realized I couldn't do that I dropped the idea)
I did think earlier though about the hallow spreading though. Apparently in the new update, hallow still doesn't convert jungle because the two would rather coexist? Not entirely sure of the details, but since corruption and crimson can still spread through the jungle, I thought it'd be fun to imagine if hallow gained the ability to specifically spread through jungle biomes that had been corrupted. As if it was doing it specifically to reclaim the territory that the jungle had lost