Well, I'm down to two spells! :lol

I will definitely max shiver armour, enchant and fire mastery. A point or two in static, mana shield, warmth lightning mastery and frost nova. (just to freeze those enemies in my immediate range every so often) Maybe even one in cold mastery to profit best from my +skills.
This makes (at least) 75 points total. And then for the rest I'll have to decide between CL and Thunderstorm.

Thunderstorm is a "passive" spell. It's dam that I don't have to care about. But as I'm calculating with about 15 points that I'll still have left (I know, I know, I could get up to 110 points in the game - but what use is a char who'd be just perfect once she's got her last skill point but can't even survive past level 60? Moreover I don't think I'll play up till level 99! ;) I want to prove a melee sorc can become Matriarch, not design a perfect char!) And it's what the "typical" melee-sorc in the diverse articles has. It'd be the better spell insofar as I won't boost mana all that much (needing Dex way more) nor Warmth (needing the skill points elsewhere). By using that one I'd only actively cast static field and frost nova, those together with mana shield being the only drains on my sorc.

On the other hand CL has the advantage that I already have it (as prereq for mana shield), so I'd have two points more to spare for it (as thunderstorm has one more prereq as well). CL might make static seem useless but in Nightmare and Hell I killed Duriel by staticing him down a bit and then calling lots of meteors down on where he was standing (as my merc didn't survive long enough to get even one potion, I had to serve as my own tank! *shudder*)
And while CL was way cooler in D1, it still can help. Fire it a few times rapidly into melee and about half the monsters surrounding you will drop.
It does have the disadvantage of needing way more mana than thunderstorm. By using that one I'd need way more points in energy and a bit more in warmth probably. :\
In a way my personal preference is CL. It does more in the way of "a bit of melee, a bit of spell casting" what I am actually dreaming about mostly. But with the greater need of mana I'm not sure if I can afford it.

But the trouble with lightning spells is as long as they are low level with low lightning mastery, they won't do much damage. So I can only take one (and should I ever get more points than I need to max it, put the rest in lightning mastery - if I don't need them for mana shield or warmth anyway ;) )

I decided against Firewall - with the maxed mastery even at a low level - it would be nice to augment what I do with melee but it's simply the same kind of damage that I'm doing anyway with my melee attacks, and so it's useless for immunes. As I'd need at least three points (with prereqs) to get it, I think those three points are better spent in my chosen form of lightning. :\ By taking a lightning attack, I will have lots of dam from fire, some physical, quite a bit from lightning and just a wee bit from cold (shiver armour + frost nova)
Unless something is immune against fire, physical and lightning I should be able to deal with it (apart from lightning enchanted ones of course :p )

And then there's the question of the merc. As I'm melee myself, I don't absolutely need a melee merc. Still the benefit from Might or Defiance, maybe even Thorns might be nice. Or then - as I'm not needing the tank - an Act III cold merc to get some cold damage. (Although I could get that at worst by using a socketed spear with cold dam for the Act II one)

So what shall it be?
CL or Thunderstorm?
Defiance, Might, Thorns or Cold?