I usually use a kinda low threshold on other power gen like 30%-40% or so ... (especially on IME diesel generators, because i don't wanna hear them going on and off constantly), and because the active extreme reactor take a while to start, i would go with idea 4 (don't really want the reactor to start and waste fuel while it gets the turbines to optimal rpm, just to fill 10% of battery and then stop or waste power. When it starts i want it to work for a while).
btw, is the new code available to download? on your site it still says ver,4.1.
As a side note, could you make so that if yo