Eldritch Blast Metamagic

[Zaydos]

The metabreath feats idea makes sense, but how many rounds of inaction is a spell level worth? Hard to convert.

Simple the metabreath feats already mimic metamagic and valued it at 1 round/spell level.

I think the worst one I've found is Empower. With either method, that allows 12d6 at level 20.

Method one should only give you 7d6 x 1.5 or 10.5d6 not a full 12d6 as it lowers the number of dice by 2 and you only get 9d6 at Lv 20.

As for the total just think Hellfire Warlock with a binder dib already deals 14d6 per round as a standard action. This only gets really problematic if combined with something like Hellfire Warlock.

As for Quicken normally spontaneous casters can't use it so maybe you could go that route, or else the problem becomes not Quickened but Quickened Blast (5d6) followed by Empowered Blast (10.5d6).