The group that is looking for a turbo kit with an aftermarket ECU is a niche group, and those in that group would have very strong preferences on the standalone ECUs they want to use. Do you see where this is going, and how that would limit the size of potential customers by targeting a niche group?
This kit was designed for those looking to get into a turbo without having to commit to a standalone ECU, and that potentially distructive learning curve. I understand that this kit isn't for you, but I don't think they had guys like you in mind when they designed this kit. Go make your own turbo manifold!