You would indeed go broke founding those far-away cities for horses. Which means you won't even have many Keshiks, and skirmishers are no pushover. What I would do? Two choices:
- Peacefully expand. You got a nice marble spot for oracle, try getting monarchy, alphabet or construction with it. Monarchy to work the wine. Then attack with catapults.
- Found a city right next to the horses, build Keshiks, declare war on Brennus,, pillage him back to stone age (Keshiks walk fast over jungles) but don't attack. Keep building Keshiks with pillage gold, then (and here's the best part) declare war Mansa Musa, and take his cities. Use pillage gold to support CoL research. Workers? Captured workers, theology and feudalism with serfdom should be enough to clear the jungles.
I agree with the second option. Pilliage your enemies back to stone age!
Why not build small stacks (2 or 3 units) of Keshiks and pillage all improvements of Brennus land and deter him/her from rebuilding them? First target the bronze and iron mines, than everything else. As many people already stated, Keshiks are the ideal pillagers, because they ignore terrain movement costs, so they can move quickly into the mainland of the enemy. When no improvements are left anymore, spread your stack all over Brennus empire, so he wont rebuild anything. You could stay at war virtually for ever, because there will be relatively few battles and the war weariness will stay low.
This strategy has lots of advantages: It allows you to keep the enemy stagnant until you want to conquer his land. It also allows you to keep your empire and you army relatively small, until you really can afford to conquer new cities. At the same time, you get lots of money by pillaging Brennus improvements. This will lead to a high research level, while the Brennus research is crippled. Another advantage of this strategy is that Brennus land cannot be resettled by Mansa Musa or another civilization as it could be if you razed his cities.
The strategy could also be applied to attack other civilizations that are farer away. You wont conquer cities, so upkeep of far away cities is not a problem. If you are lucky, your neighbors will close their borders for this civilization, so a far away civilization cannot even counter attack you.
I tried this strategy on a lower difficulty level (noble) and it works excellent. I declared war on Ghandi and Mansa Musa simultaneously with just 6 Keshiks. I dedicated only one city to produce Keshiks while the others continued as normal. I pillaged everything and kept Ghandi and Mansa Musa down until the end of the game, when I conquered them with Cavalry. Ghandi didnt even have Longbows at that time!
Pros & Cons
+ Only a small army needed, so most cities can focus on economy
+ Low empire and army upkeep and additional income from pillaging result in high research level
+ Low war weariness, because few battles compared to city conquering
+ Unlike razed cities, pillaged cities cannot be resettled by other civilizations. The territory just stays useless until you conquer it
- Enemy starts building lots of archers, so conquering the enemy requires additional units.
- Its a bit of a gamble. The strategy will fail, if not all bronze and iron mines are pillaged early enough
LC