OK, I love playing the Spanish. Lancers, iron, great provinces, alot of flexibility as to Med/Atlantic navy, defensible provinces.
In the BKB mod (where almughavars are buildable --drool), Valencia is a playable faction with a 9 star king. Navarre is also playable. So instead of only having to contend with Almohads and those pesky Aragonese, you have aggressive Valencians and Navarrese as well. I tried focusing on Valencia last night and that 9-star king is tough.
Fighting against him makes his Spanish javelinmen fight like demons. With the 4 extra valor coming from his generalship, they tear through my units. Even though I outnumber him, he is tough.
On one battle (it takes me several to wear him down), he was isolated from his army -- far out in front, near enough to my army that his army could not help. I charged him with 6 units of jinettes and 3 units of spears. He singlehandedly wrecked these, killing over 400, even as 4 archer units pelted him with arrows. Nothing seemed to work. Bear in mind that this was my entire field army. Wrecked singlehandedly.
Then the Aragonese attacked me in Castile. Finally, defending on a hill, I can whip somebody with the remnant of my army.
Fighting 9-stars with a decent army behind them is a wonderful challenge in this game.