1. you gotta remember that we devs see the "new battle" mode as a debugging feature. the only reason base defenses are even AVAILABLE on this menu is because we needed an easier way to test the scenario.
2. in it's current form, it uses the "default base" as defined in the ruleset, you can copy/paste the base facility structure from an existing saved game if you want to try a different layout. i know this is by no means a perfect solution, leading me to...
3. i do have a "map editor" planned. please don't ask for an ETA, it's a pretty big feature, and it's fairly outside the main goals of the project.