Neirfane, I believe the reason nobody has replied to this thread is because the character you propose is quite obviously overpowered, and to a lesser extent a Mary Sue. I'm not trying to insult you, I just think it would be helpful to make a list of good points, bad points, and suggestions.
A Kender NPC would be good, but the game cannot display "Kender" for his race, you would probably have to choose between Halfling and Tiefling, and have the NPC explain that he's actually something entirely different. If you choose Halfling, he'll be able to use Mazzy's bow and sword (which would be inappropriate), and if he's a Tiefling, he'll be able to use Haer'Dalis's swords (which would be somewhat more appropriate).
Meeting him by discovering that he's Pickpocketed you is a nice idea, and as far as I know nobody's done it yet. But the fact that he's a Kender means that he's not from the Prime Material, and therefore would most logically be found in a place with interplanar traffic: The Planar Sphere (the most likely spot, considering some Dragonlance characters are already there), the Planar Prison, possibly the headquarters of the Twisted Rune, or maybe even Ust Natha (as crew/passenger/stowaway on a Spelljammer ship). None of these locations seem very conducive to him casually walking up to the party and helping himself to the contents of their bags.
Additional note regarding stealing Kalah's Lamp: It's generally best to avoid making your mod depend on another mod, even one as universal as Unfinished Business.
Banters: Viconia has spent decades (centuries?) honing her skills of scathing social repartee against a healthy slice of the most insidious minds in the Realms. So if your character is able to best her in a duel of tongue-lashing, you had better have a DAMN good reason why.
Immunity to Fear would be a nice trait for a custom NPC, and of course perfectly appropriate for a Kender. But there needs to be a downside to keep the character balanced: For example, I once designed an Elven Assassin who was heavily into Poisons, way more than even the standard Assassin. She had spent years slowly building up immunities to just about every known toxin, with the result that she's immune to the Poison effect and has 90% Poison resistance. The drawback was that all that time poisoning herself took a drastic toll on her system: She has only 5 Constitution, and truly lousy hitpoints because of it. For your Kender, I would suggest that due to his size and frailty, both his Strength and Constitution be no higher than 11.
Random Pickpocketing of NPCs: A fun idea, but very dangerous, since even with a Pick Pockets score welll above 200, there's always a 1% chance that you'll Fail, and you'll have some very angry townsfolk on your hands. Make sure this is in an AI script that the player can turn off, or change to another, less volatile one.
Immune to Level Drain: Too powerful an ability without a balancing disadvantage. Also, what's the reasoning behind him having it?
Use Any Item: Way, way, WAY too powerful an ability without an appropriate drawback. Again, there's no reason for it.
Can cast spells from all scrolls: Is this character a Thief or a Bard? If he's a Bard, he'll need UAI to read Priest scrolls, but if you're basing him on Tasselhoff (which it sounds like you are), he'd be a Thief, and would of course need UAI to read any scrolls at all.
Getting his Hoopak enchanted: Not bad. A Cromwell upgrade of NPC-specific equipment has not (to my knowledge) been done.
How not to make a Mary Sue/Gary Stu: Avoid basing your NPC on yourself. Avoid basing your NPC on any character from any book or movie, unless that character is so minor that hardly anyone would have heard of them. (I once considered making an NPC Archer named Anborn. 10 points to whoever can tell me where he's from.) Avoid overly "glamorous" traits, like having the NPC be half-human, half-something really unusual (dragon, veela, troll, whatever), or having the NPC be the last of his race, or having qualities counter to his race (an antisocial Halfling, or an Elf with a long, bushy, red beard). Do NOT use Dwarves, Gnomes, or Halflings primarily for comic relief. Avoid giving your NPC eyes of an unusual color (violet) or qualities anything like "piercing," "penetrating," or "hypnotic." Avoid making your NPC a vampire. Avoid giving your NPC past accomplishments that would be wildly inappropriate for their age (e.g., being a Chosen of Tyr at 15). Avoid calling your NPC a person "of destiny." Avoid making your NPC the only person who can stop "a hideous, ancient evil." Avoid giving your NPCs powers that are either noticably more powerful than those of other NPCs, or are not adequately explained by the NPCs personal background.
Now, not all of the above qualities will make your NPC immediately suck. Giving your character one or two of them, in moderation, can actually make them quite interesting. But if you go too far, you're likely to create something like one of my favorite animated GIFs (I'm paraphrasing here): "Hi, my name's Lily, and my character is Lillandra. She's 3112 years old. She's Harry Potter's sister (I've changed the entire Potter family to Elves). She's married to Legolas--they have 5 children. She can travel in time--but it took her FOREVER to master. She can change herself into any animal. And best of all, she is NOT a Mary Sue!"