You really have to laugh at Gilles Duceppe's response to Stephen Harper's suggestion to cut the GST:
Gee, what would the world look like if the federal government transfered tax points to the provinces? It would look like a cut in the GST (on the federal end) and an increase in provincial taxes (on Quebec's end). I.e., the Prime Minister would do exactly what Stephen Harper is promising to do.
What Gilles Duceppe really wants is for the Government of Canada to keep collecting 7% GST and then sending even more money than that to Quebec. The federal-provincial "fiscal imbalance" is a joke. It is just a Quebec bargaining position, used to make requests for money sound like there is a justification behind them.