Because her people cannot. [There's a faint edge of 'like I just said' in his voice, at that.] Or had you meant to ask at the reasons they lack the ability?

[Which he is also more than willing to get into, should Tony have any particular interest.]

And you are free to do as you will with the designs. I cannot guarantee any modifications will see use, should I manage to return to the world from which they have come, but I can hardly stop you from making them.