Not sure about Turrican, what made it great was the fact it was 2d.... Anyway, it would still look cool in 3d, with deathmatch and all the funky weapons and powerups etc. There's just a few too many FPS games out there (Unreal etc) already.
Imagine though an FPS deathmatch set in the "Aliens" inspired levels of Turrican II, or even atop a futuristic train a la Turrican 3?