Starting with Exceptional Attribute, for Magic 7 and Spellcasting 6, with a specialization in whatever spells you care about most. That's 15 dice without much effort.
Elemental Focus is another +2. Rating 3 Power Focus, Rating 4 .Spellcasting Focus for your specialized class of spells makes another +7.
There's 24 dice before spending edge. If you can swing an Edge 6 human with Magic 7, then when you spend edge, you're throwing thirty dice to cast your spell. With explosions. Ignoring limits. And then you die of drain.
As stated. Foci don't Stack. ANY of them. Not just those 2.
Also, Adding Elemental Focus is fine for a Combat Caster but if your specializing in any of the other 4 Spell Types that won't stack.
I can't say I'd like that kind of character myself.
Way too "Glass Cannon" for me.
You've shot a lot 1/2 your starting Karma for 1 die & lost a point of edge.
Dice pools that big means Overcasting is more dangerous than ever.
Investing in A-Magic, & at least C in Cash & Meta leaves you with crap for Attributes & Skills which means your unlikely to be able to do anything BUT cast spells & once the shooting starts the concept of Geek the Mage is even more important against a guy with 20+ dice pool.
I'd be a lot more inclined to go with something like Magic-C, Attr-B, Skills-C, Cash-D, Human-E & have a much lower dice pool of 14-18 depending on spell type.
At Chargen, the 2 casters in our last group had Combat Pools of 14 & 15 and they could dodge with pools of 14 & 10 when they were getting shot at IIRC.
They rarely had issues with connecting with a spell & dodging at least the 1st round of incoming fire.