As long as you are strict with the skill change limitations, it's not a huge thing.  But shapechangers tend to have a social pyramid (which most characters don't take, so it's always good to have a Face) and a combat pyramid, which everyone has anyways.

Why not just let the character turn their pure mortal into a shapechanger?  maybe they get cursed or learn a spell from someone or find a Tome of Magic etc...

Then you don't have to introduce a new character.

Way ahead of you.

What's so broken about werewolves?

I've never felt the need to houserule them, so I'm not quite sure what problem you're looking to solve...

If it has to do with Beast Change skill-swaps, you could change the rules for those. Saying that no skill can change by more than 2 would leave you with a significantly weaker but not worthless Power.

I think IIRC there were those that felt the radical skill swap was out of balance.

FWIW, I was thinking exactly along the same lines you were.

My 16 y.o.son joined my game(his first ever RPG).  In the last two sessions, he's added his fair share of rib-ticklers:

1) "Well, the guys on bikes staqrated shooting at.  We tried to get away, but couldn't so we ran them over. By the way, that was the driver's decision, he totally was the guy that made that decision."--As told to the police.

2) Player A to him via cell phone:  "Do.Not. Engage."
Him (to driver): "Run them over.  No, wait, don't run them over!"

3) Me:So, the cops want to know why you had a shotgun AND a .357 Magnum in your vehicle while visiting a city park."
Him:"I wanted to go duck hunting!"

I'm glad you enjoyed yourself.

This is why I find the Resources skill to be frustrating, personally. It comes attached with zero of the many, many real-world issues and realities that crop up when you're laying out exorbitant amounts of cash, and trying to include those issues diverts the entire game in a way that I don't care to spend my time GMing much. I'll be honest, "I bribed the local police chief $50m" is just absurd on so many levels. Players try to buy their way out of every situation--how BORING. Heavy Resources use ends up turning a game into a Batman comic book, minus the cool parts. Maybe I've never had a high-resources PC that had a player who understands how money works, but so far I haven't had a high-Resource PC that I particularly enjoyed GMing all that much.

Last time I had such a PC, he often wound up bankrolling the rest of the party and rather resented it when I Compelled him. After that, I mandated a Resource cap of Good(+3) for all my games since.

Under the RAW for such items,the item is good for only a single exchange (or two or three,depending on Crafting stuff) and that's it. 

How does the community feel about an enchanted item that only bestows a single trapping of a skill, but for the duration of an entire scene, especially the social skills or non-combat skills
Examples:
The Riding trapping for the Survival skill,
The Tracking skill for Survival skill.
The Detect Lies trapping for Empathy.
the various trappings of Rapport and Intimidation as well.

I bring these up since using the social skills and the others listed above is really what I'd call a 'long action' that takes more than an exchange or even a second, but several minutes or more of work.  At the same time, I don't think this necessarily displaces Stunts, as these items can be stolen, lost, or otherwise neutralized.

We call it 'Mission:Impossible' magic. 

Down side: Not a lot of flashy KABOOM! magic (unless you are trying to make humongous nine shift lightning rings, but we self-censor for that).  In any event, if ou wanted to do that, make a conventional mage.
Up side: Lots of applications for non-combat purposes such as an enchanted item for Rapport, Burglary, Stealth, etc. that a wizardly 'secret agent' would find handy plus you still can have a couple slots devoted to quick getaways (instants five-shift smokescreen! or still manage a quick KABOOM (instant five-shift fireball--ten shifts if you take your time and roll well).

For that matte, you could go crazy and make a really kewl Warden-type sword of your very own choosing (the Stunt: Occult Lore from the wikia resource page is a MUST for that purpose). 

I think it's a far better match to what potestas was trying to nail down without blowing up the game. 

I don't know.  Is this option available for 'cosmic vending machine' rituals? (ie. can my Pure Mortal walk around with a Walker in his back pocket?)

I'm gonna pit my Denarian against your Skinwalker!

I would be wary of some of the powers from the powers list of the wikia resource page--there's a good reason it says "not play-tested for balance."  Otherwise, what everyone else said.