Ok, now I see. That is a tough one, as I would be concerned over time with that joint. Not so much from the weight of the contents on the shelf, but more so just from the weight of gravity on that joint. Any tenon or dado will not have the best surfaces oriented for gluing. No matter what you do there will be end grain involved with each mating surface on the glue joint (except at the very ends of the stopped dada or tenon), no long grain to long grain mating surfaces. Now I understand the thought behind the foxed tenon. So I think we all would agree a stopped sliding dovetail would work great, but I'm assuming you don't want to see the joint on the one side that is not stopped.
I really like the idea of a few smaller through tenons wedged and finished flush with the top, that would work very well and would be pleasing visually, but it also seems like you might be against that also.
A domino would shine here for this joint, it's really what most guys would use that are making furniture for a living and I think it would do very well. But with that said, if you don't have the domino.....
My other question is how set are you on that design? If the vertical support went from top to bottom, and wasn't suspended, then you've eliminated the problem, the vertical piece would be supported and you could do pretty much anything like a stopped dado for that joint and get the clean look you are after
I remember when I did this. The only way it worked was to stack each completed cabinet and cupboard in our living room. It took me about six months of days off to finish. Then I took a two week vacation to rip out the kitchen, do any repairs and then put it back together. Refrigerator was on the back patio and we used our Coleman camp stove to cook.