Updating iOS for offsite iPad

Situation is that iPad is not on premises with Macintosh. It's a long story, but basically the iPad is being used as a remote video phone.

So when semi-annual updating and backup are performed, the Mac is (not too conveniently) packaged and carried to location to the iPad. It's reverse portability, but necessary because iTunes is needed. The Mac goes online at location by tapping into the iPad as Personal Hotspot. Mobile service is, of course, limited in data allocation per monthly fee.

And so updating all apps can be done prior to packaging the Mac.

But updating the iOS requires a huge download.

Is there any way to "preload" the latest iOS in iTunes for one particular device?