i have heard the idea for being able to start at any town, but while it is a good idea on paper, to put it into effect is gonna be hard since the leveling of wilds at different areas with have to be different for each person at different areas, and there is the matter of not being able to go to certain areas because you cant surf or use stuff like rocksmash or cut.  it would be hard implementing this idea is my point

I do not think that any generation V pokemon should be included, this basically means the ones from black and white.  I have played these ones, and they really ran out of ideas.  Plus, i can forsee that there will be major lag, so this may help you, if you dont include the 150 new pokemon.