I'd want at least 14 con for the extra surges / HP, plus hide spec at paragon.
I'd probably build a 16 STR / 18 CHA (16/14/13/8/10/18) D'Born Dragon Sorc.
Level 1: Leather
After that it's hard to say... if there are actually good feats in PHB2 / Complete Arcane for offense, it might be temping, but on the other hand, defensive feats open to us:
Light Shield
Heavy Shield
Hide
Weapon Prof: Parrying Dagger
That's +6 AC from 5 feats (including leather), which ought to get you strong enough to survive the front line. Admittedly 5 feats is a crapload. So don't take them all if you don't have to. The sword & board fighter has 7 (scale) + 2 (shield)... [we ignore advancement, with AV armors it scales about the same]. We start at level 1 (assuming leather) with 5 (leather + 3 STR). So we need more (all of the above) to catch up, or we can aim for something a little lower, since normally I figure being 2 behind the fighter is good enough, since the mark will offset it. But you could build this as a serious tank if you wanted. And you might want to with all those close bursts.
As far as powers go, I'd take Dragonfrost over the wizard's Ray of frost any day. Push 1 is often as good as slow. Lets your ally use a move action for something other than shift.