Nitpick/"Chapter Types": Hmm. I'm inclined to say that at that point you would kind of be cherry picking your options. If I want a sneaky shooty character like Lias Issodon to be a member of my otherwise stabby chapter (using, let's say, white scars tactics), then I can...
A.) Take him in a different detachment and pay a small unit tax for some tacticals or whatever that he hangs out with.
B.) Ask my opponent if it's cool for me to scribble out his chapter keyword and write in "white scars."
C.) Homebrew a similar character that meshes well with the rules I'm using.
D.) Accept that limitations are (theoretically) part of what makes a given faction interesting. Dark eldar would be a bit less dark eldar-y if they could benefit from the powers of Eldrad Ulthran.
While I'm completely fine with saying, "This guy that looks like Pask is Commander Al'D'Dakka," part of me also chafes just slightly at taking a faction-specific character in a different faction just for mechanical benefits. I sometimes feel that that's a sign that the character is too much of an auto-take or too thematically appropriate to be tied up as a special character instead of a generic choice.
Superheavies: Fair enough.
Air Defense: I see your reasoning, but I still feel that
VP-related bonuses vary in usefulness too much depending on the mission and potentially cause big problems if you're using these rules with custom missions. You're already encouraging them to attack flyers by giving them advantages that only work against flying units, and a list built with this regiment rule is probably going to want to go after flyers anyway. You don't field the tankbusting army when you're in the mood to kill lots of ork mobz.
This is a quirky regiment choice. I say give them a quirky bonus that will be fun to use even if your opponent didn't happen to bring any flying units.
Demi-humans: Ah... It might be outside of the scope of this thread then, but I don't suppose there would be anything stopping us from writing rules for an auxilia-heavy detachment.
Cavalry Regiment: I like that! Does the secondary bonus warrant a price increase for such units?
Shock Regiment: I like this too! I'm not sure the Undisciplined trait is strictly necessary though. Fluff-wise, any relatively early real-world armies are still capable of receiving orders and executing complex battle plans. Wave a banner or give a vox to a specially-trained prim worlder, and you should be good to go. Mechanically, their benefits make their infantry really solid melee choices, but giving up overwatch and
FRFSRF probably balances those benefits out.