In 1170, our people are obviously tremendously impressed by the worker I just built, because they give us about ten palace improvements in a row.

I've never seen that before...
In 1190, an Arabian fleet, which I had assumed was carrying a settler, drops off a very scary invasion force (two horsemen) by Varna. I guess Abu wants out of the gpt he's been paying us. I don't really have much choice other than to ask him to leave, and he (of course) declares. So we're at war with the Arabs. We do get an elite cavalry out of the deal, though.
That puts our treasury in danger of going broke, but I discover that we've been shipping Spain horses and furs in exchange for just wines and figure we can do better. So I renegotiate, and Izzy is willing to throw 39 gpt into the deal. So that solves the budget crisis, at least for the moment.
In 1200, we receive word that Egypt has been destroyed by the Iroquois. Spain has most of the former Egyptian cities, though.
In 1210, Medicine comes in, and it looks like we have a monopoly. I trade Medicine to the Iroquois for Steam power and Hiawatha's entire treasury (1032 gold). It turns out that we have no coal, but Hiawatha has an extra and is willing to sell it to us for only 9 gpt. So we can build railroads, at least for the moment.
Spain has Industrialization, and is willing to give it to us for Medicine + 110 gpt. Ouch!

But I do the math and decide that it will only slow down our run to Sanitation by two or three turns, and we really could use factories. Hiawatha wants 200 or so gpt for Ind, so we are getting pretty good value from Medicine here. So I decide to go ahead and pay it.
I order up a bunch of factories (well, OK, four) and set research to Sanitation at max (at -150 gpt, so we'll have to turn down science in a few turns).
In 1220, some gpt deal or other expires with the Hittites. I investigate the possibilities and discover that he's willing to give us 46 gpt for Medicine. I figure this probably increases the chances of another sneak attack down the road, but we can really use the money, so I take it.
My prediction comes true even sooner than I had anticipated, as in 1240 Mursilis drops off a knight and MDI next to Nicaea. I had seen the ships, but Isabella had a couple of fleets in the area, and the colors are so similar that I hadn't realized these were Hittites. I don't have much choice but to boot Mursilis, accept his declaration of war, and mop up his forces with a couple of cavalry.
In 1250, Spain declares war on India.
No screenshot, because nothing much has changed. Sanitation is due in 8 or so, but we're running seriously negative gpt, so it'll actually take longer.
It looks like I messed up the Hittite situation, as we got almost nothing for Medicine.

Sorry about that. I guess trading techs to weak nations for gpt might not be such a good idea after all.
Note: We have some incoming Arabian bogies north of Constantinople; they're probably going to land somewhere between there and Nicaea. But there's only one galleon, so the ground forces shouldn't be anything we can't deal with. But it might be time to poull in some of the troops that are guarding the distant portions of our island.