RP a Wizards circle that got thrown into Grimrock.
However attempting to recast spells for 4 mages has become such a hassle I had to stop playing, my mouse finger was actually getting sore.
Technicly its not broken yet.. so I lied

Fix
A little icon in the hand when you have selected and closed the rune menu showing ice/flames/lightning/Rock so you know what spell group the spell ready to cast is from and clicking on it casts the spell like normal attacks untill you change it or put a weapon/item into the spell hand.
This will also let mages have 2 spells ready one in each hand/wand.
Another option would be to make scrolls with spells on them when placed in the hand automaticly cast the spell when you click on it like a normal attack, and allow mages to scribe scrolls.
Thou that may take more programing.
I wouldnt mind if spell cooldowns were increased if you think its imbalanced and took into account the time it takes a person to reselect the runes for the spell, its just tedious currently having to do it every time you cast the same spell in a row.