Their was some speculation that Vaders suit would be a prototype design for ROTS during filming. Whether it was really considered or just a rumour is anyone's guess, although their where some pretty convincing drawings and old EU illustrations flying around the net at the time. I remeber one that looked pretty cool was a bit like an old fashioned frogman's respirator and big red goggles, the head was unprotected ie just bald. Looked Good!!