This could be done with a series of nested SUBSTITUTE() and/or REGEX_REPLACE() functions to replace the rich text placeholders (after Airtable converts them to plain text) with HTML tags. I’ve done stuff like this for clients on occasion, and it works well.
Rich text fields use a form of Markdown syntax. I use a script that converts Markdown to HTML for my clients. I usually have the script triggered from a button or as part of an automation script. Depending on what aspects of rich text you use and how they are created, this method is a little more robust than SUBSTITUTE or REGEX_REPLACE. For example, a markdown converter script can handle reference link, as well as inline-links.
Is there any way to purchase/get access to that script? We don’t have the capacity to learn a scripting solution at the moment, but have lots of content written in Rich Text that won’t parse to our WordPress page unless we convert it to HTML first.