Ensuring a particular attendee gets into meetings....

I would love to hear suggestions on my particular issue....

I often co-host meetings with guest speakers that are open to a large audience. Sometimes when there is a speaker who attracts a lot of people we reach the 100 attendee limit before the speaker has joined. I have thought of engaging the "Waiting Room" but I'm not sure if there is a limit on the Waiting Room as well? If the Waiting Room fills up before the speaker joins I don't know how to get them in.  Any thoughts?