Decks of the Week links with Pact Belcher:
http://www.wizards.com/Magic/Digital.../tourn/1373742
http://www.wizards.com/Magic/Digital.../tourn/1373746
I personally think that, since the deck is already vulnerable to counterspells, adding Pact would make your games 2 and 3 worse against those decks. The decks in those two events had 3 others which ran countermagic, though I don't know what exactly that represents.
It does smooth out the manabase for sure, since you can get +G or +R (or fixing), but I think it would make recovery very difficult and require card disadvantage on the player's part.
Also I don't like Birds or Street Wraith in Belcher. :P
EDIT:
Well actually now that I think about it, Summoner's Pact does allow you to play through Daze a lot easier as well. For me though, Belcher is enough of a glass cannon, and pushing it more in that direction might do more harm than good.