I cannot, in any way, shape, or form support Street Wraith's inclusion in this deck. This is a deck in which mulliganing is VITAL - much more so than most decks. Street Wraith can only increase the difficulty of the your mulligan decision making process. Take this hand for example:

LED
Land Grant
Rite of Flame
Rite of Flame
Chrome Mox
Elvish Spirit Guide
Street Wraith

I would be forced to mulligan this hand. You?

How about this one:

Petal
Empty the Warrens
Chrome Mox
Burning Wish
Simian Spirit Guide
Tinder Wall
Street Wraith

Do you keep this? Your decision is much easier if you knew what Street Wraith was going to cycle into, wouldn't it? And what would we be replacing Street Wraith with - probably Dark Ritual or Wild Cantor. Wouldn't either of those cards be better in the opening grip than SW?

Essentially, SW takes a 7 card hand and turns it into a 6 card hand with a mystery card. I personally don't feel like playing guessing games with this deck.

Although SW can be imprinted on Chrome Mox, I'm not so sure that I ever would do that. I would probably always cycle it to get a red or green card to imprint or simply a better card.

In Belcher, Street Wraith is a weak card that only negligibly increases your chances of getting your better cards. As of now, I see no room for Street Wraith in Belcher.