I'm not sure what you mean by "too high level to be scripted"
You can always add spells to the script as long as the cast has at least one in all the necessary paths. They won't be cast if he doesn't have the levels/gems to cast them when the time comes.
Strange I was convinced that only spells 2 level above caster level appeared in the list (has it been changed or was it my imagination ?). Anyway you're right all can be scripted.
It may be a confusion with the ability to cast spells just researched in the turn (using the (cast) order or after the script).