Since canonically Ignis does get back the ability to tell light from dark, I'm thinking I might just have to do a prompt during the month where he realizes (thanks to the sun rising again) that he is seeing more than just blackness.
We don't know when it happens in canon, just that it does and it's been several months since the injury now. It seems a fitting time for him to notice.
I'm probably going to have him using the camp at the waterworks as his base unless people need him somewhere else. That way he can provide food/drinks/medical attention and all that.
He will be connected to the Murmur though, so people can call for him if they need him. I have a feeling he may be using his reverse time abilities a lot this month. LOL