A strawman deck consisting of 10xVillage, 10xMerchant, 1xSilver [...] Is that it?
You're narrowing in on the key insight.
Experince suggests that the straw man deck, suitably un-strawed, is more relevant than I thought. I recently played the following board: Chapel, Harbinger, Merchant, Moneylender, Remodel, Throne Room, Council Room, Market, Sentry, Artisan.
After a few losses with me playing CRoom/BM and whatnot, I put together the following winning deck: 10xMerchant, 5xMarket, 5xSentry, 1xArtisan, 3xSilver, 6xProvince, 1xDuchy, 1xEstate. My experience while playing it suggested to me that Merchant as a source of money is probably a fine idea. Maybe the reason I discounted it at first was that I underestimated how quickly you can pile up on those when they only cost $3 (and you have some +buy); I probably undervalue cantrip coppers a bit. IIRC, I added at least one Sentry relatively early, which helped me stay thin and cycle a lot.
Which leads me to think that maybe the right way to go on the titular kingdom is Moneylender/Silver, then get Merchants very aggressively, enough Villages for all my terminals, an Artisan on my first $6 turn, a CR on my first $5, Militia on my first $4 or when drawing deck, then more Merchants, throwing in a Cellar at an opportune moment. Maybe one extra Village (above my terminal needs) in case I want to Artisan-gain a terminal mid-turn?
I'm not sure I like Harbinger as a trashing accelerator: I need to draw it in the right order vis-a-vis Moneylender, and once I draw deck reliably it becomes a do-nothing cantrip, except it can play tricks with Cellar (discard something useful, then pick it up later), but that seems very marginal. I think Cellar would be a better trashing accelerator: play all available cantrips, then mulligan if Moneylender is not in hand; I think that would trash Coppers faster.
In the limit, the stop cards should be Moneylender, Militia, Artisan, Silver, 3xEstate, plus whatever greening I have done. Of those, I want to play Silver, Artisan and Militia; the rest can be discarded to Cellar. Spitballing, that sounds like two Council Rooms should be sufficient in the limit, perhaps with the aid of a Throne Room and 2xCellar?
Comments are more than welcome.
(Discussion about why my deck was suboptimal on this new kingdom is also welcome, if you feel like it.)
However, a starting hand with only Throne Rooms, Festivals, treasures, and green is a dud.
All those plurals means you start with 7+ cards in your opening hand

in my Good Stuff deck, TR+Festival plus any two treasures other than Copper+Silver (5/6 chance of getting something else) gives me a province. Hardly a dud turn for a deck which is strategically equivalent to Big Money, I would say

But of course it doesn't kick off an engine, which is your point, and that I agree with

perhaps [they] have more in common than they have differences.
The thing is, the elements they have in common are strategically relevant and the difference they have is superficial.
I like the qualitative distinction (strategic relevance) better than my vague quantitative distinction, "more".
Except for the cost, Festival seems better than Silver. Agree/disagree?
Well, yeah. But the fact that it does cost $5 and not $3 is super important for big money.
Is that because the opportunity cost of Festival is a Duchy? If so, it seems like there should be a sweet spot in the mid-game where you still want to build, but it's not so early that $5 is out of reach, where you might get a Festival over Silver and have the price not be an issue. Except that this window is so narrow that the resulting Festival/terminal-draw ratio will make it likely that you will draw it dead, in which case you should've had a Silver.
Is that approximately it?
Just CR sounds pretty good. [...] Yes to everything.
Cool, I appreciate the confirmation :-)
Also, why is the engine best here?
Mostly because you get to play a Militia every turn and that almost kills big money [...] outright.
[...] Militia makes you want to ask "is there any way I can avoid playing big money here".
Oh yeah, there's that

Once again I appreciate everyone's thoughtful responses :-)