What's wrong with a big Union Suit butt-flap?
The washing machine underwear might be the best answer, because it would seem that wiping etc. would be pretty hard even if you had some kind of zip out pouch in the crotch and butt that would catch feces, that you could then sort of air-lock it out of the suit, keeping clean afterward would be difficult.
And even if an astronaut didn't have to defecate or urinate, you can get swamp-ass in the region anyway, so having the space suit give you a rinse and a dry every 3-4 days could be hugely beneficial. If you've ever done a long cross-country car trip, or intercontinental plane ride where you're stuck sitting for the better part of 24 hours, you already start feeling "not your best".
IIRC, the Apollo astronauts found defecating into the plastic bags taped to their butt, with inward facing plastic gloves to keep everything moving "away" to the bottom of the bag so disconcerting that they all just got "camping constipation" for the mission's duration. IIRC, they weren't fans of popping the Mr. Tydy Bowl blue stuff packet and kneading everything together in the bag once done either.
And Rev's comments about the food. I'm not sure we've made any externally provisionable spacesuits either, maybe a water/liquid tube, but that's about it.
Hell, done right, might even solve the whole "space shower" problem too. Just put on the space suit, and run the whole thing through a wash and dry cycle. Done right, it could make use of the thermal control tubing that's in the undergarments anyway on "open loop mode". While normal EVA cooling is handled on "closed loop mode" etc.
What really impressed me was the cutaway drawing of the PLSS packs for Apollo, the whole O2 tank was just a little thing the size of a bowling ball in one corner of the pack. The rest of it was all the other environmental control and power systems. I presume more modern Shuttle and ISS suits are the same way.
