I always pre-build a palace when needed, but the AI tends to research techs in a balanced fashion, and not beeline towards something like I do, resulting in a long time for them to catch up to where I want to be.
I generally ignore everything at the bottom of the Middle Ages tree, except maybe for Engineering if I'm at war (for traveling across rivers), and race for Education & Banking. Then I build Universities and Banks and trade for anything that I feel that I am lacking. From there, Economics is only one tech away and waiting for the AI to catch up would mean having to wait until the Industrial Ages, like you said. Free upkeep for Marketplaces, Banks & Harbors, etc. are a big deal to me and add up very quickly. My goal in the Middle Ages is to research and accumulate wealth as quickly as possible.
My biggest problem with Emperor is keeping people happy early on.
Yeah, keeping the people happy is a task to be sure. I have a four stage process that has been working very well for me for larger scale anything-but-culture-victory games. There are certainly other ways to go, but this one has been serving me best lately, as long as I get a half-way decent start (maybe two food bonuses in the FC):
Stage 1 -- A Happy AA. Turn off goody huts. They only help the AI on monarch and up. With militaristic or religious civs, I've been having a lot of success in researching the south side of the tech tree and trading backwards. The secret is meeting other civs early and trading your starting techs for theirs. Then the trip to monarchy is fairly quick, and the computer will sell ANYthing for polythesim and monarchy which are almost always my monopolies. Your cities only need build rax and units.
Don't be afraid to make raids on your weaker neighbors; pillage their roads and take their workers/settlers wherever you can. More slaves = more infrastructure for you = faster city improvement + 0 upkeep on workers + time for your cities to build anything except workers. You don't need to take their cities yet, but if you can get away with it, do so. Sue for peace if they retaliate in numbers. Enter MA.
Stage 2 -- The People Love You... or Else. Switch to Monarchy and build LOTS of units to keep the your ungrateful minions content (three

allowed with units per city), since you mostly don't have much else to build at this point. Build markets, libraries, and aqueducts where needed. With one or two luxs, the people stay plenty happy and productive. If they get out of line, turn some into settlers/workers. Research toward Chemistry. Start prebuilds for Leo's and Cope's.
Build rediculous hordes of horsemen, swords, and pikes. Expand outward, and take your weaker neighbors' cities when you build more units than are useful for content faces. Use the swords and a few horses to attack soft targets. This helps expand your borders and it takes surprisingly little to cripple your neighbors at this stage, once you take their cities, workers, resources, and techs. Also fish for MGLs
Stage 3 -- A Step Ahead.
Most of the other civs race toward astronomy, notable exceptions being the ones with gunpowder UUs. Because techs get cheaper as other civs research them, and because the AI loves gifting each other, the top part of the tree gets researched almost as quickly as you alone could do it. While you are researching gunpowder, most of the time education will come available, as well as chivalry if the knight UU civs are out there. Trade backward for both, uprgrade all your horsmen to knights and the occasional pike to musket for frontline defense (you
did build Leo's, right?

)
Stage 4 -- Reap and Sow. Make your neighbors into dead neighbors. This is the BEST time to spark your GA if you have a knight or gunpowder UU. Why? Because universities, banks, and knights are expensive, lots of premo wonders are available, and you have lots of newly conquered cities to improve quickly to make productive. When better to do this than during your GA?? Since you already have most of the bottom of the tree (and hopefully got an SGL for you C3C people), trade chem for astronomy (or just demand it from a civ after taking most of their cities), switch a prebuild to Cope's while you get physics and ToG, then build Newton's. Since you are in your GA, the rest of the required techs go quick, and sometimes you can get steam power quickly too. Rail everything.
Happiness might become a bit tough at this point, unless you have been able to conquer some luxs. I combat this by turning a lot of my larger cities to settler output and use the settlers to resettle all the AI cities I've razed. Use the happy slider if need be.
At this point, you've started the avalanche down the mountain. Your civ should be untouchable. The major downside is that if you worked over your neighbors too badly, they won't be able to contribute anything for the rest of the game, save for useless techs like printing press and free artistry. Cripple the other powerhouses by selling them something like Steam Power for 500 gold + 60 gpt. In the game mentioned above with the sword vs inf, I'm researching radio as the last IA tech, and none of the other idiots would even have industrialization or medicine if I hadn't sold those to them. Consider also that I let my governers manage the city citizens. Imagine what I could do as a micromanager
If anyone else has a strategy they like to use, I'd like to hear it. This one is getting old, ha!
