I'm not. But you're not going to get it faster with constitution than mids no matter what you do, unless you don't have the mids

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I have no idea what you just said.
I don't know what kind of improvement/city combos you're using, but...what? Why is it that an empire with 1-3 solid cottage cities can't match (or come very close) the bulbing of an empire that runs scientists everywhere?
I'm sorry I don't answer why questions.
Anyway this is a fact that's pretty well documented elsewhere.
It's going to be hard to get more than 1-2 EXTRA scientists by running multiple sources of GPP vs just one.
It's not hard at all, I do it most every game. Either
- you're not trying,
- you're doing it wrong (for example, building too many wonders), or
- when you run a CE you really run what I would call a "SE with a few cottages" (Dave's thread here (Dave correct me if I misrepresent you) is to suggest how to maximize your cottages -- which you aren't doing if you're running a ton of specialists).
A balance of commerce and specialists will blow out either 0 bulbing OR just running scientists exclusively, unless you have pyramids, but then why are you prioritizing constitution over something like biology?!
Please explain how you would balance the two and how that results in a "blow out".
What qualifies as very early?
A lot earlier than it can be had while working mostly cottages.
You can get it in the early AD's anyway.
That statement is relevant only in the context of a specific game.
We're playing fast and loose in terms of what the hell CE and SE are in the first place if we're going with this type of discussion. This article mostly highlights how to use cities set up for commerce via cottages. The terms CE and SE are detrimental, especially to players trying to learn how to play the game, because they suggest excluding specialists or the use of commerce. Clearly, you're not doing this if you are running a suped up commerce bureaucracy capitol in your "SE", you're taking advantage of all the improvements, which is optimal. CE and SE are misleading then though. Where exactly would you draw the line between "CE with a GP farm" and a non-rep "SE with cottages"?! It's preposterous - better to look at the yields cottages and specialists give us and how to balance them optimally without using "CE" or "SE", which would save a lot of grief and newbies figuring out what the hell people are actually saying.
Ok, where to start.
"SE" and "CE" are labels for strategies. And those strategies are not "specialists to the exclusion of all else" or "cottages to the exclusion of all else", although as I read Daves guide I believe he encourages the latter somewhat more than most people would. Which may be why he mislikes the "CE" label -- because his "cottage economy" is more CE than most CEs.
In any event, your "clearly" statement, as most such, is anything but. A SE as I mentioned does not mandate specialists to the exclusion of all else.
What you advocate is that all games are hybrids. Which, to anyone but a purist, all games ARE. So, of what use the labels? They're shortcuts to allow us to have intelligent discussions without having to go all the way back to 2+2=4. To me, SE means I get most of my research+maintenance from specialists. CE means I get most of my research+maintenance from cottages. EE means I get most of my research+maintenance from espionage. Etc.
Research+maintenance is the thing upon which the game revolves. They are the things every player wants, whether they realize it or not.
As for the use of a bureaucracy capitol in general (aka a side note):
In the time frame where bureaucracy is most effective, it is ~usually~ best to emphasize commerce.
That's arguable. For example, if you have a lot of research+maintenance through other means, then you may value hammers quite a bit. Having a wonder- or unit-producing capitol can be huge.
Most any player will admit that a 1 hammer is valued much more than 1 commerce. Just go read some of the threads about the 1:1 ratio debate, productive/stone/chop -> gold exploits, etc.
Most of the time, however, the commerce is flat out more attractive for bureaucracy.
In the context of this thread, I totally and 100% disagree. Dave (as I read him) advocates mass advancement of cottages across multiple cities. This means a hammer capitol w/Bureaucracy would be a very strong tactic... if not essential. Basically, you would probably have to devote 3 production cities to make up for your 1 capitol to be a cottage city instead.
I'm not saying it's a definite thing. But it's a powerful tactic and fully an attractive option. Certainly not "flat out more attractive" as a cottage capitol as you say.
If, however, we ignore Dave's advice and run the "same old" CE as most people run, where we do not maximize our cottages, then maybe so.