Nearly every enemy mage that I encountered had all of these cool spell triggers and contingencies, and I kept thinking "I can't wait until my mages can do that. It will be fun to play around with different contingency and trigger combinations." But alas, it was not to be. I completed the game without access to chain contingency and timestop (except via scrolls), and I think that my mages had almost hit the EXP cap, so I doubt that such spells were attainable without removing the exp cap. It was quite a disappointment. I would have much rather have been challenged by increasing the number of enemy mages that I had to face, or giving them better fighter support, rather than by having them tease me by weilding magics that my own characters will never get.
This brings me to my next point: Why have experience caps? Unrealistic and silly, if you ask me. If an enemy spellcaster can reach X level, then why can't my own? There has not been many places in the Baldur's Gate series where monsters will respawn, so it's not like a player can go "power-levelling" anyways. I suppose that a case could be made for soloers, but come on, this isn't Diablo! The game was meant to be played with a party, and I see no reason why the gaming experience should be degraded for those of us who like to play the game how it was originally intended, for the sake of a handful of people who don't like to utilize the available resource of NPCs. Besides, better fighter support for enemy mages would likely offset the benefits a solo player would gain through having a character that is double the level that a PC in a party would be, since there are no saving throws vs melee attacks.
By the way, am I the only one who found it quite odd, the high number of powerful archmages in BG2 that were employed as common thugs? I would think that such powerful mages would rather spend their time persuing knowledge, than working as door guards or goons for criminal organizations.
