Jerseys are a lot like bicycle frames. All bicycle frames should have as many water-bottle mounts as the tubeset allows. All of them. This doesn't mean mountain bikes shouldn't have any. Or fixies. Or single-speeds. I would even go so far as to say TT-specific bikes should have them. The cyclist has the option to use them, or not. Put cages on, or keep your frame bare and clean-looking. Whatever you want, but ALWAYS give me the option.
Jerseys should always have three rear pockets. Three. Always. Period.
Mountain jerseys, too? Yes.
Skin suits? That's not a jersey, that's a skin suit. Pay attention.
I might never choose to use them, but I always want the option. Also, two tiny side pockets with a normal middle pocket doesn't count. I want three BIG pockets on every jersey. If you choose to make one zippered, or add a fourth zippered pocket, that's just fine. Give me my three normal ones, though.
Coming soon, I'll be posting a review of jerseys (corresponding to my review of bibs). My feelings on this matter just might come through on that review, so I thought I'd prepare the few,stalwart readers of this blog in advance.