What would the path be had you been able to contain the light?

[Jandor]

I mean, we did contain the light, right at the end. He even gets a brief glimpse of us as we were. His response is to turn into a giant monster and try to kill us.

Still though, if we had been able to contain it earlier and have a sensible chat about things, I don't think his overall plan would have changed much.
The part of the plan where they kill everyone on the Source after the shards have been rejoined might have been scrapped, but I doubt there is any version of the plan where Emet lets the reflections survive.