While asyncio's naming is somewhat confusing with all the get_event_loop, new_event_loop, get_running_loop() etc and I like the leviathan.Loop() syntax, having a drop-in replacement would be nice, so especially a leviathan.get_event_loop would be a nice addition.
Further shipping a custom event loop policy would make it very easy to use leviathan with asyncio. Like
import leviathan
import asyncio
asyncio.set_event_loop_policy(leviathan.EventLoopPolicy())
so asyncio would use the leviathan implementation under the hood (from my understanding, but you will most likely know more about this)