If you’re using 365, OneNote can sync to the mobile app and vice versa. This will all depend on how your company sets up MDM\MAM but if the 365 suite is MAM enabled you could install that on your personal iPad. You wouldn’t be able to copy to\from your physical device, but everything is synced up to SharePoint so that’s all you would need access to.

How do you imagine this working differently to what you could do at icloud.com using the online Notes app?

EasyCanvas supports a one time payment model but seems to be focused on drawing instead of note taking, and it's not clear if the files would be stored on the iPad.

Why can't you enable VPN on the iPad? Oh, are you saying it has to be wired to join and can't be on wifi? If so, I believe you can use an ethernet adapter. I don't know the models that would support this, but I confirmed they do exist.

Any chance work will issue you with a Mac? This would be so much easier if they would. You'd be able to use the iPad as an external display for the Mac, and could run Mac note taking apps (which save all their data on the Mac) on the iPad screen, with full touchscreen and pencil support for drawing/etc. The iPad basically becomes a Cintiq.

I think the only way Windows can connect to an iPad over USB is with "iTunes File Sharing" which requires installing iTunes on Windows - then it will be able to access some data on the iPad. It used to be pretty widespread for note taking apps to support that, but I'm not sure how common it is these days. Almost everyone uses cloud sync these days.