Since no one else has replied ...
Personally I'm a fan of the troll mage archetype. As you've figured out the, only really effective way to do it in the priority system is A Metatype, B Magic, C Attributes, D Skills, E Nuyen. If you an do sum-to-ten you have a little wiggle room (you could drop skills to E and up attributes to B, or whatever), but its not really necessary.
To get down into the crunch:
Magic
Be a full mage. Aspected Magician sucks.
Special Attributes
Edge is great, but a high magic score is more important. So you'll want to use 2 of your special attribute points to boost Magic to 6 - the rest can go into edge (which still gives you a very respectable edge score).
Attributes:
For a troll mage with an intuition/willpower tradition you'll want the following:
MOST IMPORTANT - Willpower of 5
MOST IMPORTANT - Intuition of 5 (this is the one stat you'll max out)
This gives you a drain dice of 10, and uses up half of your stat build points.
As you're a troll you might as well take advantage of your high body score and start with a 7 or 9 body (an odd score is optimal here). Though if you don't care 5 body is more than good enough for a mage.
Beyond that everything is up to you. If you plan on taking longarms you'll want a few points in agility, of course.
Strength, Charisma, and Logic are your dump stats - beyond roleplaying purposes they serve no purpose for your character.
Skills:
Your skill layout is solid. Maxing out counterspelling is also worthwhile. Beyond that:
1-2 points in assessing (more isn't necessary, really)
1-2 points in perception, you don't have room for more
1-2 points in sneak
1-2 points in etiquette
For the 1-2 point guys you can easily spend 2 karma each for 1 point. You should have the karma budget for it.
Qualities
Witness My Hate is worth it
Uncanny Healer is meh but sure you can fit it in, no problem
Definitely get a Mentor Spirit. They are well worth the 5 karma. Just make sure you're OK with the downside, because as a troll you're almost never going to make the roll to avoid it.
That gives you 24 points of positive qualities.
Day job and dependent are point hogs for negative qualities, and you can always grab a few more low-key ones like allergy if you'd like.
Spells
You'll get 7. I'd recommend lightning bolt as a damage spell (fries drones), and maybe stunball. You'll also want some utility spells, there are tons of great ones. Levitation, Imp. Invisibility, trid phantasm, detect enemies/detect life, chaotic world, improve reflexes (or whatever its called) - all great. And of course Heal is spectacular.
I'd recommend picking 2 combat spells you like, one aoe and one direct, and heal, and improved reflexes, and 3 other spells of your choice.
Improve reflexes (or whatever its called :p ) is actually very important, as you'll have no other way of boosting your initiative.
Gear
You should have the karma to get the 20k extra starting nuyen. Your number one priority is a force 1 sustaining [health] focus and some reagents. You'll want to be casting the improve reflexes self boosted with reagents into your sustaining focus before fights. You should easily have the karma to bind such a low-level focus.
Next priority is a solid fake SIN and fake magic license (at least rating 3, preferably rating 4).
Next you'll want your lifestyle, which will also be pricey.
Then you'll want your armor, your gun, and some ammo.
After that, if you have any money left, you can grab 'nice-to-have' things, like contact lenses with vision enhancement built in, or earpieces with audio enhancement built in, or misc. things.
Sadly you won't have the money for a combat spell focus, but such are the sacrifices of the troll mage.
Overall
You should be just as strong a caster as a human/elf mage, though your drain dice will be slightly lower (humans usually have 11, elves usually have 13). The trade-off is that you should be much tougher, especially if you boost up your body.
A secondary non-magic combat skill (like longarms) is usually a good idea for a mage, so you have a backup if the background count is terrible or there are other circumstances that make casting undesirable. You won't be great at other skills, but your magic should help supplement there.
The one thing you really lose out on as compared to a elf/human mage is starting with a high-powered focus, but thats unavoidable (and doesn't impact your core functionality).
