Well caves still don't produce darkness, so it would actually be kinda meaningless.
The Exile series of games are excellent and have been remade as the Avernum series. I advise anyone interested in the setting to give them a go, because they really are top tier RPGs.
It seems ver. 3.15 broke some things in the mod. I noticed the national spells are not available after upgrading. For example, mages that were order to cast "Gate Troglodytes" before the upgrade are reported after to upgrade as casting "gift of flight" and the nation summon spells are not available to cast.