I think the complexity of the design would depend on what you want it to be: From a practical point of view you can make a simple design if you consider it like a glorified shoe tree, not that it can't be an attractive shoe tree.

Now if you want it to look like a person wearing armour and posable then you would need a more thought out design.

A nice shoe ( Armour ) tree would work for me and if I built something it would probably be using a minimalist design using 2"x4" glued in a cross shape with a lower cross piece to suspend the legs.

Now with either more time and money to spend on it I might go for expensive hardwoods or have it custom made or look for something already available out there.

But a simple and functional structure is all I think I need as long as it gives me a nice way to display and store the armour.

At the moment my armour tends to clutter up my bedroom floor the pieces stacked next to each other.

Oh, I like it to much to just shove it in a closet ......... LOL.