After further consideration, I think all ship construction should require varying amounts of all three materials.
When you build a space vessel you're not only building a hull. It takes design, planning and administrative resources, as well as labor and materials.
I've always thought construction in SEIV should simulate this by making greater use of the "other" two resources, especially organics. I've played so many games where I've finally built resource converters and the only thing I use them for is to convert my huge surpluses of organics and radioactives into minerals.
Ideally, I had hoped SEV would be more like SEIV, only with more resources to mine (and maybe produce!) and more political depth.
