Opinions about tenting angles are very subjective. I find that 15 degrees is more than adequate for me. More may be slightly better but not worth the negatives that come with it. Negatives like awkward transitions to and from mouse, bulky look on desk, and gravity working against you, all added up to me deciding on the more conservative angle.
Well, I think anatomically tenting angles are objective, but then of course it's personal preference if you need/want/like it or not. I find that if I write a long session on a flat keyboard, then afterwards my hands feel a little numb until I shake them around. With enough tenting this problem is reduced significantly. If you place both your hands on the table in thumbs up position, hold there a while, and then tilt thumbs pointing at each other flat on the table, do you not feel an increase in tension? I find the tension begins around half way, with anything below that feeling almost as bad. The lower the table is, the less the impact.
I can relate to your negatives, but IMO the positives outweigh the negatives, I guess this is the subjective part. As far as bulky look goes, I've toyed the idea of getting a semi thick piece of sheet metal, drill holes and shape to match the ergodox case, then bend the metal sheet to create an open wedge. If necessary, add flat supports running inside against the wedge to improve the solidity, while keeping an open design. For wrist support you could add a raised flat surface in front of the keyboard, somehow matching in design, for a place to rest hands. If done professionally this design could look good on any modern table.
