Discussed this with @Juul briefly, sharing his experience writing hacks for authentication across all the systems at Labitat.
Given that it was a pain in the butt and took a bunch of time, at the very least it may be worth it (in the long term) to use Mozilla Persona to hack auth into all of our apps, instead of writing independent little hacks. Either way it's a lot of work, but it may be better than the alternatives. Definitely not the most immediate priority, but I think still worth keeping our eyes on.