Arelith

We already have this kind of synergy in regards to Spellbound Wands - a caster with an applicable metamagic feat will apply it to the spell inside.

The same logic could be followed regarding their big brothers, the Sequencer Staffs. Wards with a duration would benefit from Extend, damage spells from Empower/Maximize etc.
An interesting aspect - that might also need some balancing tweaks - is that this would enable spellcasters to apply metamagic to 9th circle spells, which is not normally possible.