The position of ISO left shift is terrible. ANSI/ISO both have terrible right shift. JIS right shift is comically absurd.
Furthermore, no key except possibly the spacebar should ever be wider than 1.5u. The ANSI right shift’s 2.75u width (let alone the WANG/Kingsaver 3u right shift) is some kind of joke.
Putting shift directly to the sides of the pinkies (where ; and caps lock are, respectively on an ANSI/ISO keyboard) is really nice. Shift on thumb keys is also pretty nice. Shift next to the home position for the index fingers (where G/H is in QWERTY) takes moving all the letters around, but is also pretty good.
My “standard-ish” QWERTY proposal (for folks unwilling to use a split column-staggered keyboard):
Implementing a strike-style instead of hold-style shift also can advantageous for both comfort and speed. That is, pressing and releasing shift and then pressing a letter will capitalize it, instead of needing to hold down the shift key through the letter key press. Alternately, another reasonable idea is a “post-letter modifier shift”, where you first type a letter, and then press the shift key to toggle its capitalization. Or even type a whole word, and then repeatedly press the shift key to cycle capitalization (lowercase, first letter cap, all caps) on the whole word.