A spacecraft is a pressure vessel, and the smaller it can physically be, the lighter it is. Clearly, a space-suit is the smallest-possible pressure vessel that can carry a human and still have them operate external controls. (you could make a LIGHTER one-man capsule if you discarded the arms and legs, of course - something like a one-man minisub with external manipulators, but then you become totally reliant on power and the electromechanical linkages to perform survival functions - "open the Pod-Bay Door, Hal.")

If you have to carry a space suit for emergency purposes and/or for EVA/surface excursions, it makes sense to put as much of possible of the main ship functions inside it, and reduce the requirement on total pressurised volume of the main ship. And yet, if the suit is only an emergency one, then everything has to be duplicated in the main ship, and a larger suit needs a larger ship to carry it.

The options you describe seem useful, but one can already sip liquids and food concentrates within an existing suit. One doesn't need to get a knife and fork out and have a folding table and full dinner service (and where do you fit the microwave oven and fridge? 8-)

I guess if you can dispense with the pressurised cabin entirely, then you're getting somewhere useful - the Russian one-man lunar lander was unpressurised and relied on the pilot's suit for survival. This way, you also get round the problem of bringing surface dust into a shirtsleeves environment.

Personally, I'd go screaming mad after 3 hours, let alone 3 days, in a space suit - but the astronauts and pioneers of the future will be chosen for their tolerance of confinement, like submariners today.

It'd also stop all these rumours of sex in space, unless you fitted some very interesting docking hatches!