I have both and the KD is maybe 1.5 times the size of the mini jypsiere by volume. I'll take a side by side photo when I get home.Thanks for highlighting @fonnas' post.
I've been thinking of the Kelly Depeche 25 as a clutch and shoulder bag as well!
Noticed that it's (relatively) the same size as a Mini Jypsiere, except one could switch out the strap more easily on a KD -- so that's a huge pro for me, aha.

So I did just order one of those sangle connector thingabobs from Etsy and I happened to see an etoupe Kelly strap on Fashionphile, so I grabbed that. I tried it out last night and it is very cute as a cross body bag. The strap is standard Kelly length so it hangs high, so I might get a longer and thicker strap to go with it. I will post mod shots when I get home.