logically posts or custom posts should be available in more than one spot.
Somehow I think you said that wrong, because by design (and intent and logic) CPTS are separate from posts and pages. Otherwise you would have used them :) I see what you're saying, but basically you're thinking about CPTs the wrong way.
That's why there's no built-in (though you can implement it) crossover tags and cats, too. You CAN pull normal cats and tags and custom taxonomies into your CPTs, but they will always show up separately and that's by intent.
It's not how permalinks work, it's how CPTs work.