If it was me, I'd keep an eye out in the For Sale section of forums for anyone selling a K03S second hand. Also, if you're getting CR Turbos to do the hybrid work they ditch the compressor housing altogether so you can use a K03 which are even easier to find. PM me if you want to know where to get one from.
You'll be strangling a hybrid on the standard manifold and downpipe but technically there's nothing stopping you doing it. Bear in mind that the map would need adjusting once you had fitted all the necessary uprated items. In an ideal world you'd be better off waiting until you have all the parts and doing it in one hit.