Forgotten characters busting out into their own adventure for glory and recruiting side characters from the main series sounds exactly like Nippon Ichi’s style of meta madness. Besides, a great way to redeem Taro’s character. Either he’d need a big character boost… or he’d make a great gatekeeper!
Demon Lord (Hanako): Adell's sister who earned a new title. She set out on her own
Hanako’s perfect for this—especially since Hanako was already shown to be a powerful Demon Lord 10 years into the future. This could easily retroactively fill in that blank. (Disgaea 2 gets overshadowed everywhere it turns anyway.) Plenty of room for multi-netherworldal shenanigans here with other characters after their games, especially given Hanako’s known to be a powerful summoner. Zany chapter 1-1 nonsense like “Oops, I discovered reverse-summoning and got myself summoned to another netherworld for a fight and back… so I, uh, kept doing it…” sounds like Nippon Ichi’s MO.
We’ve already got a sequel in Disgaea D2… go for sprite models, call it Disgaea 2D, and ship it.