I liked this idea enough to give it a few hours of thought and testing and came up with the following:
Vintage Combo Shadow
1 Mox Emerald
1 Mox Jet
1 Black Lotus
4 Mox Diamond
1 Lotus Petal
4 Chrome Mox
2 Overgrown Tomb
1 Bayou
3 Tarnished Citadel
4 Death's Shadow
4 Street Wraith
4 Berserk
1 Spoils of the Vault
4 Plunge into Darkness
4 Once Upon a Time
1 Vampiric Tutor
1 Mental Misstep
3 Tainted Strike
1 Snuff Out
1 Force of Vigor
1 Gitaxian Probe
4 Thoughtseize
1 Imperial Seal
1 Demonic Tutor
4 Land Grant
3 Reanimate
Sideboard
2 Gurmag Angler
4 Leyline of the Void
3 Force of Vigor
3 Veil of Summer
2 Surgical Extraction
1 Duress
As per the original idea the goal is to play Shadow as quickly as possible and then kill with it on your next turn.
Manabase: The goal was to consistently play a Shadow on turn two and win with it the next turn. To do this the deck needs two or three permanent sources of mana for the entire game but the earlier you can put them into play the more likely you are to play a shadow on pace. I went with only BG colors because while the blue cards are powerful, they don't really contribute to our turn three kill plan. Tarnished Citadel a card most people have likely not seen is the best land to put into play as it allows us to take three damage each time it is tapped, the two copies of Overgrown Tomb are there to both damage us and to be found by Land Grant and finally the singleton Bayou is for situations where we cannot afford to take damage, also a good land to pitch to Mox Diamond to slightly increase the chances we find a more painful land.
We play the on-color Moxen, Lotus and Lotus Petal as part and parcel of the Vintage fast mana package. Rounding out our acceleration is the full set of both Chrome Mox and Mox Diamond which while costly allow us to consistently cast our spells and convert unneeded pieces into mana. I would caution people picking up this pile from mindlessly playing out either Chrome or Diamond without considering what you gain from them as they are useful when the accelerate you into something meaningful but can be a trap if used without a purpose.
Finally, we have the playset of Land Grant and Once Upon a Time, these spells will help ensure that we find the lands we need and fix our opening hands. Pay attention to both the restriction on a free OUaT and Grant when assessing an opener, specifically you can use Street Wraith before casting OUaT to gain more information and can use Mox Diamondwe in addition to your land drop for the turn to ensure that Grant is free.
Lifeloss and Utility: To Play a Shadow on turn two or sooner we need to be able to lose at least eight life in those turns, and to kill we will usually need to lose 17 or more life. To do this, profitably, we have a number of cards that both disrupt our opponents (Thoughtseize), cycle to find our own combo pieces or provide mana for ours spells. Street Wraith does double duty as a cycler to find what we need and pinging us for two, it is also good good friends with Reanimate as cycling a Wraith then brining it back puts us to 13, just one life away from being able to cast a Shadow. It is also important to note that Wraith attacks for three which can be an important part of dealing 20 damage and winning the game. As I mentioned earlier, Tarnished Citadelis one of our best ways to lose life, if we land it on turn one we can hit ourselves for nine by the time we are killing, it is a good idea to play it early and tap it aggressively. Tomb does something similar but only once, and is a necessary evil to support the Land Grant. Plunge, Vamp, Imperial Seal and Spoils are all very similar for our purposes as they are going to find a missing piece of our combo and lose us some life along the way. Vamp is the best for pure tutoring while Plunge gives us the most control over out life total. Finally, we have our two 'blue' cards in Misstep and Git Probe both of which are too good not to play and a way to lose some life and gain some value. Snuff Out has been fine for me, you could easily replace it with an Unmask or a Surgical in the main.
Combo: This part is fairly simple, we have the full four Shadows and Berserks as well as three additional similar effects in Tainted Strike. Remember that you can double up on Berserks and even combine it with a Strike if your life total is too high.
Conclusions
This deck functions as advertised, it plays a Shadow on turn two or earlier and kills on turn three or earlier when it isn't disrupted. It loses to itself infrequently (missing on Spoils or something similar) and certainly feels unique. That said it doesn't hold up well to disruption, lots of the Xerox decks are going to overpower a single discard spell and counter our Shadow. PO has been a coinflip in my experience, on the play you are fast enough to beat them and a single discard spell is often good enough. Shops is better that it would appear and usually they will need a good hand to keep up. BUG is unwinnable.
Play this deck for the novelty, I would say that the above list is a good start if you want a very combo oriented version, but do not expect to run the table.
As ever I am happy to talk theory and testing with anyone who is interested in the list or the logic that got me there.