Might be worth it to set up a little lab? There's no Formidable documentation regarding Stripe Terminal, but you're looking to build a solution and since there's integration between FF and WooCommerce, you could get a WC extension that supports Terminal (YiTH and Arcane, for instance), and the use Formidable to make your custom WC forms. I did one for a mobile food service and the biggest challenge was the receipt printer. They didn't want to use tablets in the truck, and wanted little paper tickets like in the restaurant. Zapier, a cloud print service, and a wifi-enabled receipt printer were the fix for that. Again, a little lab might be the thing.

The Stripe Terminal API docs say, "You can build with our server-driven integration (US only), or with a platform-specific SDK using Android, iOS, or JavaScript." Since you can use JavaScript, you can integrate with Formidable. There's also a list of approved card readers.

Thanks everyone! Looking in to this now!