While there aren't completely armorless models, there are a number of normal "bare" heads included on a number of space marine sprues, as well as chaos space marines with different naked bits (arms/tentacles). So, while there are probably a number of "hoses" and whatnots associated with the suits, and probably a number of Inter-venous hookups, the suit wouldn't be like on a turtle and required to survive.

While there aren't completely armorless models, there are a number of normal "bare" heads included on a number of space marine sprues, as well as chaos space marines with different naked bits (arms/tentacles). So, while there are probably a number of "hoses" and whatnots associated with the suits, and probably a number of Inter-venous hookups, the suit wouldn't be like the shell of a turtle and required to survive, more like the shells of Hermit Crabs ;) ALMOST vital, but able to be removed for maintenance etc.