A set of manifolds with a cross over pipe for a big single. The manifolds are all the same, the cross over pipes are the same on the manifold ends, but have different flanges for different turbos. This would allow you to use ONE SET of headers with multiple cossover pipes/turbos as you upgrade turbos. Make the manifold ends the same flange whatever flange you'd need for set of small twins so you have that option available too.
Build this. Charge 600 bucks for the headers, 150 per cross over pipe. Get rich, make power. Done.