Griffyn, mate... you really lack in the "techno romance" department.
Certain machines... just bend the rules of probability and casuality even in the mundane real life (See older Toyota Hilux, 286/386/486 computers, F4 Phantom II, UH-1 Iroquois,  Yamaha YBR 125 ( ) and so on and so forth) and others have a mystique about them (Choppers, Cheap Steel Asian-American Defence Implements, Bullwhips) , although unexplainable.

It isn't hard to think that a trusted iron steed that already possesses both of such qualities, could/would become much more in the "magic is real" of the Dresdenverse.

A slight deviation from your original theory;
it doesn't have to be TTH that does the 1-2-3 on your list.
One of the complications of TTH's mission might be tracking down another time traveler, albeit one that is... suffering from certain mental issues, ala hallucinations and being lost in his/her own mind/imagination... Imagine someone trying to stop evil Harry doppelganger thing from luring Murphy (or someone else) into a trap, except the idiot isn't ware that it's in the past and targeting the wrong thing and mucking stuff up on an impressive scale...

I would advise you to place a few unrelated hooks here and there for the group to stumble upon. (like a barfight for the bear, a contract or an eviction notice for the potion maker and so on) to get the things rolling. Let the party stumble around a few natural / slightly friendly locations like a bookstore, netural pub etc with some low grade "quests" like a pickpocket or such to ease them into the system. Then get the storry rolling and put them against a (slightly supernatural assisted) gang to defend some place.
The party should be pretty strong  with a planned defence and some prep so it shouldnt be too hard for a first run.

Don't be afraid to cheat if things don't work out. fiddle with the dice if your bad guys are too strong foır the party. Also don't bother with detailed plans. Just wave "a good story" under the reporters nose and some books for "the hedge wizard" and "sorcerer". They will pull the party along in no time. Just don't be obvious about the carrots you show to the party. Let them "evesdrop" on a secret conversation about the old books or newsworth story or plain old cash .

Personally, unlike other sponsored magics, I don't allow my players any access to soulfire or hellfire alone. Sure you can use re-bar alone as a tool in a pinch but you need some concrete is my reasioning.

Granted I haven't run many games with soulfire in it but in the few instances where soulfire was on (temporally) the table, I slapped a mild or heavy consequence (or a temp. aspect) onto the character that used it. You are emptying your life/chi/soul to do the job after all.

It might be a bit rough but I think 3 uses of soulfire per session is over doing it if it isn't about to end a story arc (major or bigger milestone), 2 is barely acceptable in a heavy action session.

You have to remember that it probably took Harry a week or more to get back "full" use / dexterity of his right hand after he used it to soulfire his grabbing spell. That stuff can literally leave you paralysed you after 6 or so spells.


*On the other hand, I actually encourage my vic.. Player(s) to use hellfire. I pay him fate points just to have him empower his spells. At no cost to him. Too bad that I am still waiting untill it accumulates something like 10 to 15 debt. It will be really nice to supercharge one of his spells with something like 10 fate points and accidentally wipe his allys and friends during a battle. 

A micro travel sewing kit with a few additions like a small magnet and a bone needle and so on.
An adjustable key chain yoyo.
A Magic Marker
Pen, little notebook, small pencil with eraser top
a quill sharpening knife (a very small knife)
A McGyver knife (Swiss army knife in other words )
A keyring light
Candles (Tea and 1 Hour types. Preferably non parafin, ie edible, ones)
A cheap disposable plastic lighter
A high power cigar lighter
A small ziploc of salt
A small ziplock of iron fillings
Holy Symbol
Focus item(s)
Chalk
A few Crayons
Energy Bars
Play doh



There are a few more things that would go into my magic on-the-go bag but these are the barebones I guess.

 Ps http://www.jimbutcheronline.com/bb/index.php/topic,19512.0.html

If a magic-crafter lends a magical item to a pure mortal (like a protection charm or a potion or some such. Like Harry lending his duster to Murphy for example), mechanichally continuing to pay the refresh cost himself, then the mortal will still have his +2 mortal refresh. If the mortal took up the magical item to himself (Murph taking up and accepting to use the sword) then s/he no longer has the +2

On a semi-related topic, there is also the second tier "elements" like Cold (Air and Water), Entropy (Water and Spirit/Force), Growth/Wood (Earth and Water)... What can you come up with?