I made glass body parts but they look solid in game.When you edit your blockhead It looks like glass.
It's not possible to have transparent parts other than the helmet faceplate and the feather. You can however, do this with bot events. Use setAppearance and set all nodes color to the transparent color of your choice. The results are interesting to say the least.
off topic- is your avatar a blockhead or minecraftian? lol