JPEG originals save as DNG ... ?

I'm wondering ...

Some of the sessions that my wife does in her business, especially during her children's specials is shot JPEG rather than RAW. And when we shoot country-club memberships, it's also shot JPEG for immediate sales. We wish to of course have a "protected" original for each image shot, so we create an "archive" folder for these images and created jpeg's from them for later sales and retouching saved in subsidiary folder structures.

It does get confusing, especially when de-duping ... what's the "original" or just a copy/derivative, as within our major workflow jpegs are always just a derivative made from the original RAW.

I know that DNG's would take more space ... but I must say ... I'm wondering whether to convert our shoot-in-jpeg session to DNG before beddin' 'em down. Would take a bit more space (though with the proportion they are to our "normal" trade, very little extra really) but ... it would be OBVIOUS that they are "orginal" work and of course, we could get 'em "hashed" for quicker verification in the future, besides having the "corrected" preview of the file as worked in Lightroom.

Thoughts. opinions, idle irrelevant chit-chat?

Neil