Exactly. I already made the mistake of even suggesting I MIGHT be willing to do work for someone who had no idea what they wanted, but wanted it very specifically. It's not one I'm likely to repeat, as migraine headaches and trying to avoid screaming at someone online aren't my idea of a good time.
If you want this done, have a plot, background, unit specifications, and, well, pretty much everything else done beforehand, and ready to go. Or, alternately, take what you can get and work your ass off to get the dozens of completely different model styles (all serving the same one or two specific functions) to work together. Don't say I didn't warn you.