If memory serves, Bioware kinda stopped anyone adding more metamagic effects.
I think it would theoretically be possible if everyone used the new spellbook system, but as it is wizards, clerics and druids do not. I suppose that could be done, but it's no small change. Then there's the issue of actually implementing the effect, which would require modifying every single spell script that it could possibly be triggered on. That's definitely possible but time-consuming.
If you just want the effect, it would not be terribly difficult to create an items and scripts for each persistent spell you want that you could just shove into your override folder and spawn in-game - providing you're not using the bioware spellbooks to cast. If you do, things are a little more difficult but it could still be done.