I too am feeling the sting of not being able to more rapidly be able to build up my civilization.
I was always under the impression that by buying a building or unit, and a city building "Wealth", that those cities were building parts, and buying was assembling them. But they've removed that impression now, by making it possible only with an otherwise useless civic.
So I've considered what the original poster has considered: that it should be possible to more directly share production between cities, but I fear that that would upset the balance of the game, and I'm in a minimalist mood. Couple this with my feeling that Universal Sufferage shouldn't be where it is; instead, it should be an optional aspect of other civics.
Basically, this is a group of special civics that are not either/or, but instead are all yes/no. Each has benefits and problems, moreso than the other civics. Think of it as the income laws you can pass in Sim City 2000 (legalize gambling and crime goes up; enact 1% sales tax, commerce goes down, enable parking fines to reduce traffic, people get unhappy when public transit isn't sufficient, etc). This particular civic would become available with, say, Replaceable Parts.
It's unfortunate that it's a bit more complicated, but if it corrects my perceived flaws with the civics system, it'll make me happier.