In that case, I would expect that you still have a fair amount of available sugars for your second pitch because that is a very big job for one vial to handle. I still think you're fine with pitching the next yeast in the primary without racking, but I'm also interested in the reasons behind your process. Since you're re-brewing this beer, I assume the first batch turned out great and you want to repeat it, is that right?
One reason I can see for taking the approach of using one yeast to start fermentation and another yeast to finish it out would be that you want the flavor profile provided by the first yeast during the lag phase, but you want the better attenuation provided by the second yeast. For imperial IPAs, usually the flavor contribution of the yeast is hidden by the hops, so most brewers I know use a large pitch of a very attenuative strain (like 1056) to get the beer to dry out in one shot. Then again, if this process turned out a great IIPA, I wouldn't want to mess with success.