Just like finding items that cast spells at higher than their innate level, could the scribe scroll function be modified to allow casters with meta magic feats to scribe at a higher level if they scribe an empowered/extended/maximized spell? For simplicity, it could be set to scribe at whatever level is innate, plus some fixed number, just to represent the greater "umph" put into it?
If the argument is that all "umph" comes from the caster's innate power during a normal casting, not a scribing, that's fine too - just an idea.