[LintMan]

Here's an alternate SC you can use for Arco:

Ghost King
Air 3
Water 2
Earth 3
Death 3

This leaves you 230 points to spend on scales, dominion (base 3), castle, and perhaps even some extra magic skills as you'd like.

Those magic paths allow you to cast:
Quickness
Ironskin (and later Invulnerability)
Breath of Winter
Mistform
Mirror Image (or perhaps Soul Vortex later)

The Ghost King has some nice built-in advantages over some other SC pretenders:
- he's undead, so he gets: 100% cold/poison res, disease immunity, and best of all: 0 encumberance, so fatigue worries.
- ethereal
- cause fear +6
- chill effect

As soon as you can research 3-4 of the above spells, he's good to go out whopping indeps, but as you are able to research and forge them. you can give him some nice booster items:
- Charcoal Shield (gives flame shield)
- Sword of Quickness (2 attacks/rd)
- Horror Helm (boost fear to insane levels)
- Jade armor (gives auto Quickness)
or
- Rime Hauberk (gives auto Breath of Winter)
- Flying Boots
- Pendant of Luck
- Anti-Magic Amulet

There's plenty of other armor choices you can pick besides those two. I mention those two because they provide effects you're casting spells for, so if you get the item, then you can script a different spell for another sort of boost, such as Air Shield if you're dealing with a lot of massed missile units.

As a side thing to mention: since you're planning to play SP for a while and said you don't want to worry about having your pretender with weak astral getting duelled, you can download the Magic Duel Mod from illwinter's site, which boosts MD's cost to 1 gem/100 fatigue, so you'll almost never see Magic Duel used after that.