It seems like a huge problem for leadership to have decided that you're just going to go 6-12 months without a CMS. If your website is critical to the business,

It seems like a huge problem for leadership to have decided that you're just going to go 6-12 months without a CMS. If your website is critical to the business, then it seems (perhaps) worthwhile to just pay for another year on your current CMS while you procure a new one. If you really can't change that, then forget about the HTML output. Dump the data from the current CMS system in some machine readable format (there's presumably a database, right?), export to Markdown, and bring it into something like Hugo (https://gohugo.io/ https://gohugo.io/). You'll have to do some work to re-assemble the site, but if you don't have a system like that, you're gonna have a bad time if you have to adjust the design of the site or something. A giant pile of HTML is really not useful to anyone except as output from a build IMO.