I think one of the problems with Nero was that people were more interested in a Vergil game or a game that tied up DMC2 so when he was introduced as the lead character and the plot of his game was announced, people were disinterested.
I feel an easier way to bring him in was just to set Nero up as Dante's kid who shows up at the office when Lucia's there, they meet up and they go figure out what happened to Dante blah blah blah.
A big issue with the story of 4 is people feel that it gives no real pay off as your no closer to understanding how this fits in the canon, nero's origins still vague, no returning character is developed, etc so my idea gives some payoff cause it allows you to explain Dante's shift and course correct it.
Plus he wouldn't be a random joe like Nero ended up being and a big chunk of why we as fans should care about him is given so its an easier sell.