I would go with GTW, but that's just me.
You can definitely do the first paragraph and have a single page. I created something similar to this article
and it worked quite well. I recommend cloning the webinars from a master program template and doing so about once a month because you'll have to update the main reg flows and page to run it.
Until Marketo sets up recurring webinar integration with GTW, that's about the best solution I've seen.
If you're using tokens smartly you won't have much problem cloning a single webinar campaign for each presentation. Then on a single registration page you can have people select which webinars to attend. Then in the flow step you'll need to use "Request Campaign" to change the status to registered. Last time I checked you can't have multiple change status in progression stages in a single flow step.
Hi Justin, we've set this up by having a master landing page with links to each webinar landing page and then create each webinar program seperately. By using tokens, you can easily clone the program and then just remove the link from the master landing page once an event has occured and deactivate that landing page for the specfic event. It also allows for the 1:1 integration with WebEx and the Event Program.