Incidentally, your DM has an... interesting view of what is balanced and what isn't.
Heh. Yes he does. I don't think the shade deserves the +4 level adjustment, especially when we have a kobold who can do an insane amount of fire damage with his breath attack, and has 35 dex. Sure, the Shade has some good abilities, but none of them are super gamebreaking, and most are only useful in running away.
He openly admits certain character builds/classes are "broken" and yet allows them, but other things, which seem less useful, aren't allowed.
All in all, though, he's a fun person to have as DM, and much more lenient in terms of weird sourcebooks or homebrew than my other friends.
Now that that’s decided, the only real choice is between ‘Ranged Sneak Attack’ or ‘Daggerspell Mage’. If it’s the former, you are probably going to want a reserve feat. If it’s the latter, you should probably be reading a Gish guide. But, to save you the time of finding one, I'll let you in on some advice, courtesy of Operation Shoestring: "Daggerspell Mage is a trap. Sane wizards keep their d4 hitdie the heck out of sword's reach."
Problem is, I'm not sane. If I were going for a ranged sneak attack build, I would absolutely drop the Shade template. Unfortunately, I'm rather attached to the idea of being able to teleport around and control light and turn invisible and other things. The guide would definitely give me a stronger character, though...
As far as the d4 goes, I'd only have a d4 for my initial level, thanks to the feat. Daggerspell Mage grants a d6. Not a whole lot better, but worth noting. The Abjurant Champion has a d10, which is definitely tempting. I guess what I don't get about that is how you're supposed to combine melee with spells there.
Additionally, Daggerspell Mage has 6+int skill points per round. That plus Able Learner is pretty sweet.
I'm googling trying to find a "gish" guide, but not having a whole lot of luck.
Would you advise against dipping into spellcasting at all if I'm set on melee sneak attacking?