Look if your determined to dispel a quickened spells there are ways to deal with serious amounts of drain. Not the least of which is just having the opposition show up with an effective magic rating equal to the force of the Quickened spell (Power Foci for example), yes that does not effect your drain pool, but going from P to S is biggest safety step. If your prepared to boost your drain stats, you can break into the 20 die range, and with planing there are ways that you could mess with concerning backgrounds.
Power foci won't effect whether the drain is physical or stun. They literally do nothing except for add dice to any pool that includes MAG-- The benefit is the fact that a
huge number of pools benefit from that.
The issue isn't if you can dispel it, the issue is should you. If you go through the method to make this happen it's going to be clear you made some fairly serious NPC(s) with a very limited focus.
Quicken spells are serious, they represent a serious power advance at the table, and require serious investment on the part of the player. Quickening in moderation, is perfectly reasonable imo. If all your player does with it, is boost init, I'd just let it go.
But if your player start getting out of hand with it, then I'd chat with them about it. If that fails, well there are ways, to achieve it.
The issue is that they really
don't require a serious investment. They require 1 Karma after spending 13.
That is not a lot. It's as much as it'd take someone to bring one skill from 6 to 7. Boosting initiative is a huge deal, I don't know how you can think going from having "solid initiative that requires a sustaining penalty or takes up a focus" to "the highest initiative in the game, hands-down, for 1 Karma" isn't a big deal. Sure, if maybe they
only quicken one spell, it's not disruptive but... The question is
why? It's a minor investment after an initial relatively low investment. If you're not specifically limiting them to just one spell, or giving them set restrictions, it's going to be really hard to tell what's going too far, and what's just the obviously great choices to improve your character.
I actually had a player tell me, even if he learned every relevant attribute-boosting spell with Karma and got dispelled every two or three runs, he'd still be fine with it because of how incredibly more cost-effective it'd be than the way anyone else could get +4 to the attributes they want (and spells can do attributes nothing else can touch, like Charisma). I really can't blame someone for not taking advantage of the just blatantly beneficial ability that's always a good choice for initiation early on (as it's powerful and doesn't scale with initiate grade). I feel like it's up to the GM to say what limits they're putting on it, or else it's going to get jumbled and the PC will either have to just choose to be less capable and more vulnerable than everyone else just so they don't get left behind. Unless they're specifically going for that "mediocre medium" kind of thing where it's like "don't be so bad you're fired, but don't be so good they ask more of you..."