Pointed Discussion

Because paying four mana for a 4/4 creature was just too powerful, it really needed that additional cost.

This would have been a cool 4/4 for 4 if it didn't have that POS ability.

You...You realize that a 4/4 for 4 is way above the curve in any color but green, right?
It has to have that ability to not be strictly better than pretty much every vanilla creature at or below 4 CMC.

Artifact creatures used to be "priced" higher (either mana- or drawback-wise) than similar colored creatures because the rationale was they had so much flexibility due to their colorless nature. Nowadays, we get artifacts with CMC= power and toughness with powerful abilities, like Wurmcoil Engine, without any drawbacks. It's powercreep, but I don't think anyone played this card in anything but limited decks anyway. Hollow Warrior does have some neat flavor, though.

If he were 3 mana he'd be excellent with Order of Whiteclay. Possible use for johnnys with untappers (Gilder Bairn for example.)

Eh. I like him, but his drawback is kinda meh. At least he's costed effectively.

I actually prefer Complex Automaton, if only because I can see him in several comboes while this guy just taps someone you control. Maybe you could use him with the shadowmoor untap guys?

It's hollow because it's a Mech Warrior, :) You need a pilot to operate it.

Cool flavor :)
If only he retained his pilot's abilities too

Can be used now to more safely trigger your Inspired mechanic.