If this happens... well, a fair deal would have to be reconsidered.
Primarily I think would be the matter of whether or not Hazou could deploy a Misterator without giving himself away. His apparent plan was to deploy from behind the pillar, then hid himself inside the edge of the mist briefly. That won't work with Line of Sight being relatively unhindered. So what are the possible things Hazou could do?
One would be that Keiko, knowing how Misterators work, would just nix the item from the plan due to no good way to deploy it. The EM plan on its own is still useful.
Another would be to ensure there's an open window, and run through the mansion to escape that way. There might still be some risk of being seen or caught. A distraction earth clone henge'd to look like someone else and a silence mine to make his own run quiet might mitigate that.
Hiding Like a Mole could be used to deploy from underground in a wide area spray, from the middle of the crowd, though this would limit the info Hazou's able to get due to being underground - he'd be somewhat guessing on the location of people. It could be done from somewhere other than our chosen spot on the porch, as well, with Hazou being on dirt from the start, but would such a convenient spot exist? He could also maybe do it under a different henge, but would need enough chakra to change henge again as well as do HLaM.
Release on a timer would work, but that'd leave the seal as evidence, which could be traced back to our group just by checking our kits. It could be destroyed with a similarly timed explosive seal, but that'd be an indicator that a seal was used, so would be an indicator a seal master (or at least someone with a lot of seals) was responsible. Also, explosives might cause a panic on top of property damage, so they're somewhat of a no go - I'm pretty sure we rejected use of explosives during planning anyways.
