I was thinking about this again. My latest idea was basically a JD45 with three straight columns thrown on the right side as a miniature number pad. I can share a layout when I have time later this evening.
The total amounts to 16 units wide & 4 units tall, but that's the smallest size I can get while maintaining proper staggering, keeping a usable number of keys (in my view), and without relegating any numbers to the FN layer. So rather than a number row, you have a number pad to the side, in a less than 65% package.