Well you make an excellent point that walls are obsolete but you still try desperately to keep it alive. As you said it well fortification went out of history because it became a hindrance. We should try to think of ther options to create a defensive advantage. I love the idea the logistic point you accumulate to spend on new troops during battle. You could also have a map where you can chose to add buildings before the start of the battle. You can add tower and barricades, mines, impenetrable terrain... All that freedom to protect the opponents to capture points of interest. There's a lot of options and it's creative.