Shandalar castle advantages

[mtk]

I like to play Shandalar with wizard difficulty. However, some castle advantages are so bad that they make the game way too easy and not fun anymore. Worst is the Blue castle where AI manascrews itself by sacrificing Islands to untap Leviathan. I was wondering if it is possible to change which cards are in effect at castles to make the game more challenging? Of course there is always the option to play the game with Sorcerer difficulty where castle advantages are better, but I wouldn't like to do that, because it affects also other things like starting cards and enemy lifepoints.

So, is there an easy way to change these castle advantages?