Hi, I read your blog post and find your situation interesting. The bias you mentioned for the Kinesis Advantage is something that also recurs in the reviews. A couple of reviews and my finding included are that the Kinesis takes time to fall in love with and not all will do so. I love my Advantage, but would not recommend it to anyone. Your ridiculously high speed of 150wpm is maybe more of a hindrance than an advantage for the adaptation, I guess. Any change in keyboard will be an added frustration since you have to slow down so much with it.
The gripes you have with placement is something that puzzles me. In also using vim profusely I swapped the esc and caps keys. Since almost all my text interfaces use a vim plugin or run straight in vim, I don't use home/end/pageup/pagedn often. End and pagedn I remapped to also work with shift. This makes ctrl+shift very simple. I also very rarely used the delete button, so delete and alt are swapped so that alt+tab and other combo's are easier to reach. I also ordered a foot pedal. I think I'll remap the function keys and some other keys onto the keymap layer (or onto a separate layer) so that working with ide's will work better. In the keypad layer I already have c,v,x mapped to ctrl+c,ctrl+v and ctrl+x so that I can use my mouse with cut/copy/paste simply. Basically the ability to remap the keyboard simply and quickly is one of the great advantages of the Advantage. The maps are also human readable and easy to backup or transfer to your new keyboard. This might be a solution for your symbols.
Your gripes about the layout, especially the ~ and the ] keys are common complaints. I think the buttons of the pinky row should be slightly smaller to accommodate the small arc of that finger. It would be interesting to test such a board to see if it has an ill effect.
I hope you find a solution for your keyboard conundrum. Since switching to an orthogonal layout keypad I doubt that I would like to switch back to staggered and don't think that it is a compromise one should make just because 90% of keyboards are built like that. The width of my shoulders make a keyboard where my hands are right next to each other extremely painful, but if you are fortunate enough not to have that problem, then you could look at orthogonal layout keyboards that ar more regular shaped. Maybe the Truly Ergonomic Keyboard, the Ergodox or the Dactyl is an option.
