There really isn't anything about spector that doesn't 'fit'... Honestly, there is nothing in the world that doesn't 'Fit' in MOTU... The line was designs for little kids... and when "I" was a little kid ALL my toys played together. He-man, super powers, Voltron... they ALL worked together.
That's why we've got Barbarians, ninjas, cowboys, robots, cyborgs, etc... EVERYTHING FITS.
NA even includes Spacemen and He-ro has a distinct 'super hero' look to him.
Granted, Spector does not fit in witht he 8-back very well... but he'd blend with NA and the later series quite easily.