Upgrade Path for '05 w/ 4.2 Nav

I have a friend who has an '05 Prius w/ 4.2 Nav. My friend is relatively non-technical, whereas I am relatively technical.

My goal is to update his Nav system for him to the most up to date available, while still maintaining the ability to read burned DVDs and bypass the inability to enter data while in motion.

I have a copy of his 4.2 disc and have saved his loading.kwi file for potential use in a 'Hybrid Disc".

My question is this:

What combination of data files and loading.kwi will give him the best bang for the buck?

He is not opposed to buying the newest update, but doesn't want to lose the ability to enter data while in motion. I would love to burn him a disc with this capability.

The real issue is that we're thousands of miles apart, so i'd like to give him a true plug and play experience. I'd love to burn a disc, send it to him and have it just work.

I've read that in some situations, it is necessary to temporarily pull the fuse for the Nav in order to rollback firmware. I'm sure that this would not be beyond him if that's part of the optimal solution, but anything more technical than that and it will require a visit.

Thanks in advance for any and all replies.