Or you size your sequential turbos so that it is pushing boost at idle.Sounds like you would have to have a supercharger or low end performance would suffer.
How would you have that? The piston is still near BDC. It's not like you're cracking the intake valve at TDC. You leave the intake valve open for a small portion of the compression stroke. You do all the 'compression' in the turbos that way you can extract the heat from it. (Unlike doing it in-cylinder)Also, you might have issues with valve to piston collision with the changes in intake valve timing.