I enjoy the uniqueness of many IC2 items and functions, and have thus decided to share an ambitious idea. What I am suggesting is a full body suit that would make the player either completely invisible, or have a dim outline. The helmet would make the head invisible, the boots would make the feet invisible, etc. This armor would, of course, run off of electricity, and slowly discharge similar to other equip-able IC2 items. I do think there should be some form of protection against mobs as well, so either mobs would be unable to see the player (perhaps only if they had all 4 pieces of armor), and/or the invisibility suit had an armor value. In my opinion, the best would be both, with a very weak armor value. Though, it would be cool if you stared at an enderman, they still attacked you, and enderdragons were able to detect the equipped player as well. Additionally, there is the issue of nameplates in SMP. This could be constantly dimmed, maybe even identical to crouching where it's invisible behind blocks, preventing the invisibility suit from being OP. Personally, I think it would be better if the nameplate was completely removed (only if the player was wearing all 4 pieces), but you could see a dim outline of those that are invisible. The recipe would definitely include at least one advanced circuit, but depending on whether or not there is an armor value, nameplate, etc., the recipe could be highly variable.
