Well I went ahead and picked up two of the Avengers Toys. Here is a shot of the Iron Man "Assault Armour". It's about 7 inches tall so I think it will make a nice light/medium sized mech. The torso and legs are hollowed out so I'm going to have to come up with something to fill those gaps but I have some ideas already. I've got the toy shown here with all the weapons but I'm only going to use a couple of them for the final version.
The other toy I picked up was the Iron Man "Firestrike Assault Jet". Apparently Iron Man likes to "Assault" things. It does in fact come with some landing gear and an underbelly turret with a pair of really big guns. I think this would be a great support VTOL for my Hell Knights for the Mech/Tank hunter role.