Would be very difficult. Jiraiya won't let Hazou invite the other Kages if we don't invite Ren, and Hazou put his foot down on inviting Ren. We'd have to come up with a good internal argument for overriding his previous conviction, and even then Hazou's animosity would probably sour the event a little.
Which isn't to say we couldn't try if we really wanted to, but I feel like inviting Ami and Zabuza is already biting off more than we can chew and I don't want to risk ruining the whole thing by putting Hazou too close to Ren for an extended period of time.