Persian War Elephants are only countered by monks. Set up your economy for elephants, and you should be easily able to mix in some hussar (not much of a tech switch since they share almost all upgrades). If you see monks, that’s what the hussar kill. If you don’t see monks, hussars raid villagers or try to kill trade, while the main push is with Eles. I know this technically uses more than one unit, but it’s the same every game, no on the fly adaptation or mid game tech switch required.
Khmer Ballista Eles make a similar deathball. Try both and see if you like either.
Mongol post imp with drill on siege onager is one of my favorite things ever. Mangudai are also good and can snipe enemy siege, but drill SO is one of the most satisfying units in the game.
Also try out hindustanis. They can be played two completely different ways (both good!) and the caravanasery helps make your trade more efficient. More gold = more fun!
Hindustani Imperial Cames does extremely well against other cavalry and is far more well rounded than generic heavy camels… they can actually threaten things other than cav with their bonus hp, attack, attack speed, and building damage. Just keep them far far away from halbs.
Hindustani is also fun to play as gunpowder civ: +2 Range HC is nice, and the +armor for both hand cannon and bombard cannon makes them surprisingly more durable if enemy dives for you.
If your other pick is flexible as well (for example Magyar with FU paladin and a top tier Cavalry archer) you can wait to see what opponents you’re facing before deciding on making camels or not. If you see cavalry civ, go imp camel + Magyar CA, otherwise go Magyar Paladin + gunpowder support.