Italy is actually relatively well served for Grade 1 circuits. Monza, Imola and Mugello all meet the specifications. However, Mugello doesn't have the capacity from a parking perspective, and the facilities aren't as plush as Bernie would like. Imola was last raced in F1 in only 2006 and has had a number of revisions since, including entirely new pits and garages installed in 2011. It's really the most ready to take over, but it'd be criminal if Monza went.
If Monza had to be replaced, I'd rather Mugello as it has some properly ace corners and elevation changes that would make for quite a challenge for the drivers and quite a spectacle too.