Trap the soul: 1 version no hit die limit
Harm: Empower damage
Slimy Doom: Add max, empower
Cloudkill: add max, empower to acid damage part
Rework charm/dominate: Perhaps dominate spells should get fewer saves
Epic destinies: make the passive bonuses per level more inclusive, for example the per level magister caster level increases should affect any caster type (Paladin, Cleric, Druid and others shouldnt be excluded). Can't think of any unbalances, just creates more customization.