Yes, but I think it is just basic knowledge. I know how to change commandsets for units, heroes and buildings, how to change the revival cost of the heroes and, through copy-paste, how to replace the skills (but I don't know how to create new ones). So what will I need?
Being more specific:
I'm making my own version of Pelargir, based on some maps already saw on Internet and in some concept arts. But I'm having a problem with the circular outer walls, because if I use the Minas Tirith's walls the circle looks too tight, while it should be more oval. Using Gondor Castle's walls it's even worse. The only way to make the wanted shape of the circle is to use Rivendell Walkways covered by two rows of Amon Sul walls. But there I find a gameplay problem, since the walkways are not climbable with Siege Ladders and Towers and, since my Pelargir is basically a fortress map, this highly limits the strategy for a siege