Honestly, even an hour of prep time would be alright. Longer prep time means that he'll likely bait Danzo into an ID. But since it takes place at his house, then he gets to play tower defense. This actually would be disadvantageous to him, as all he can do with the tower defense system is instantly spawn golems. If he has prep time, he would much rather force Danzo to breech his barrier first (Which would've taken the church of masks at least 30 mins I believe).
Still, since they're fighting outside his home, I see no reason why Han wouldn't have the same set-up as he did fighting against the church of masks. Lightning storms that will rage for 20 hours, this time concentrating their might upon Danzo, as well as golems larger than him, seeking to place Danzo inside of themselves, rendering him unconscious and allowing Han to perform Eternal Skill Theft, letting him steal his abilities and reducing him to a peak human.
Like, even with the Izanangi, it's likely going to be used up well before he even reaches Han. In particular if Han himself comes out to join the fray, with his nigh infinite danmaku, ability to nullify magic, debuff him with his realm of sorcery, and potentially control the wind in the area with Sylph, who can also be buffed. Not to mention that Han can use the magic power stored in his home to buff himself all the while.
Han's resistance to mind manipulation practically renders Danzo's genjutsu useless, and he also has telekinesis for if he decides to nullify all magic within the area. Han with prep at his home is literally made to take on an army where every individual is comparable to him. And he did just that. I don't see Danzo being able to get through all of that.
