You have a whole lot of other issues when turning an attic into living space that have to be concidered.
Main two are the access to it, and the size of the floor joist.
Then you have only 2 X 4 rafters to work with now. Not near enough room for for the amount of insulation your going to need in your reagon.
All those cross ties you have now were installed wrong anyway in my opion and are are not doing much. They were suppost to be long enough that they could be attached to the sides of the rafters not just sitting on the bottom of them.