No webex meeting is not the solution
You do not need an alternative host.
You need to connect Marketo to webex through the launchpoint connector. This is done in admin-> Launchpoint. Look to the doc here: Add WebEx as a LaunchPoint Service - Marketo Docs - Product Docs
I echo Gregoire's comment. Webex Meetings is not the right solution for this, it needs to be Webex Event Center. The intergration with Marketo is only available with Webex Event Center.
To add an alternate host, you'll need to follow the webex instructions: Event Center FAQs | Cisco Cloud Collaboration Help Central
This is more of a Webex question, so if you're having more issues I recommend reaching out to your Webex Support Contacts.