Ok, that is officially a brilliant idea!Perhaps a shadow breath weapon that emulates other breath weapons, but is only quasi-real (like shadow evocation)?
We can go with Cleon's suggesion of caster level = age category, or we could stall a few levels to have them cap out at 8th (something like 1st, 1st, 2nd, 3rd, 3rd, 4th, 5th, 5th, 6th, 7th, 7th, 8th).