Assuming a limitation of mics and inputs (e.g., four mics going into a Zoom recorder), what we’ve done in the past is just have the guests pass around stick mics. So one mic with the host the whole time (stick or lav), and then the others are stick mics that get passed around. Not ideal, but doable.
The other alternative, which IMO would be less ideal is to have one or two stick mics that the guests would walk up to.
Or, maybe put a couple of stick mics strategically placed on stands that sort of act like boom mics that can “cover” a couple people at the same time.
But agreed, a less than ideal scenario for sure. And it sounds like no matter what scenario you end up with, you can expect a lot of post work.
Better might be to break it up into segments so that no matter what you only have as many people on a mic as there are mics. So for example, four mics, host + 3 guests. Ask questions, respond, then break, reset with new guests, and stitch it altogether in post. Generally there’s only one person talking at a time, no matter how many people you’ve got. I know podcasts can be a bit different than an event, but I still don’t think you’d have 10+ people talking at once.
My encouragement would be to see what the event producer is willing to negotiate, because it otherwise sounds like a recipe for something that no one would be happy with in the end, even in a proper studio setup. Just too many people. Again, IMO.
Joby.