Alright, I can't speak for your group's rules, but I can tell you how our group plays Kill Teams, and I don't think we stray particularly far from the base-line, but anyhow:
-unit restrictions apply, so if you were buy tactical marines, you'd be stuck buying 5
-special rules that a model might be granted only effect that model - if the rule is said to effect the unit this model is supposed to belong to in a normal game, we fudge it, and apply that special rule to any model within 3 inches of the model with the special rule. (again, I can't speak to the way your group plays it, but we play KT a lot in our group, and this is how we've come to play this rule, just to add flavor and variety to our experiences)
-the specialist rules can only be taken from the "Universal Special Rules" section of the BRB, additionally, you can only take each rule once (so you can give Stealth to 1 model, and must take another USR for your other specialist)
-this probably doesn't apply, but in our group we have a gentleman's agreement to avoid units that have AV in Kill Teams. At that point scale we just feel like vehicles really skew the whole experience
-missed your some of your first post, no HQ's are not allowed - pity as I'd love to take my BA Honor Guard all kitted out, but alas..
I hope some of that helps - KT can vary incredibly between gaming groups so it's really up to how yours plays.
Last edited by mustardParty; 02-08-12 at 09:25 PM.