Suggestion: allow sovereign spellcasting in tactical battles he's not present at

A simple suggestion: to allow you to cast spells in tactical combat when no sovereign and/or hero is present.

Justification: Sovereigns can already cast overland spells, why should they not be able to assist remote units in combat? I'd also suggest it not be limited to your own borders - this will make the enemy AI's attacks more dangerous and interesting, and make magic-use more useful as a strategy.