...but, apparently, I need to spread the xp love before I can xp him again.
I agree with most of it, but not this conclusion:
Which is, again, why basing the game in "Assume there are no rules" would be a positive step. Each group can determine for themselves what elements of the rules help or hinder their own style of play, without fear that grabbing one bit of it would stop the other bits from working.
For me, though, this fails. Building up a rough-and-ready "default" set of "rules lite" procedures and mechanisms is easy, but producing a coherent set of interlocking rules that all make sense with one another and support a coherent agenda of play is
hard. I want to pay WotC to produce the coherent, consistent and interlocking set, not the "here are some neat mechanisms to noodle with" set. I already have rule sets that amount to the latter, in actual fact.
What we may need is smaller, discrete, more self-contained rules elements, that affect only themselves, and nothing outside of them. Nothing like 3e's treasure system, for instance, which has all sorts of unexpected consequences if not followed, from the skills and monsters to published adventures' encounter rates and hundreds of other tiny effects.
Fine, but what about the people who want a wide-scope game that meshes and hangs together as a fascinating whole? I mean, D&D mostly has a rather modest scope of what it does well to begin with - a deracinated bunch of (possibly golden hearted) ne'er-do-wells who have "adventures" involving "action scenes" is just assumed, at a minimum. If I'm paying cash money, I want a focussed, coherent ruleset that achieves (at least to an extent) clear design aims, not a collection of "neat ideas we brainstormed", thanks very much

.
Wandering monsters (should) make time a valuable resource, as does a reactive dungeon. Spending time searching carries a cost. Without that cost, it makes sense to "Greyhawk" the dungeon (or Take 20 on Search checks for every 5' square).
Yeah, 4E misses those. I actually think there is space in 4E for encounters that are 3 or more levels below the party level, that give no xp and that can be used for wandering monsters, failure consequences in some Skill Challenges and incidental "speed bumps" that are meant to be dealt with using no or very few resources.
(Avoiding the challenge-based play vs. simulationism issue)
There's the simple fun in making stuff up.
Sounds like the very soul of Sim, to me!
The most efficient way would be to make a random table to generate that detail (or rather steal one from the internet). Adding that detail could be done on the fly. It's more satisfying in play if the prep work has been done, I've found (eg. dropping a clue in the entry room to the hidden cache in the statue), but it can be pretty easy.
I wonder whether this might have correlated to the fact that, in the very early days, "the Dungeon" was expected to be a sprawling maze that the player characters (possibly several groups of them) returned to week after week? With this approach, the little "surprises" and "Easter eggs" you have hidden remain to be uncovered at any later time by a passing, perceptive newbie...