It would take away the point to run different networks as whichever one is made the "core" power network would of course have the most favorable conversions and thus make the other two (or more) networks obsolete. Right now there ARE conversion methods (except to Blutricity and Blutricity to EU) but they are made lossy for a reason. I really can't stress enough that non-lossy conversions would more than likely throw the balance of one or more tech trees completely out of whack and cause rampant obsolescence.
If you want a universal power network in your single player game, no one's stopping you from throwing in the power converters mod, but there's no sense in throwing off server economies severely and trivializing half the mods in the pack for one or a few people's whims.
Well that's more of a problem with the way your brain works instead of the concept. You are free to do things however you want, no sense limiting people who want to be more seamless. And it wouldn't make the other mods obsolete, just their power system. May I suggest making everything compatible both ways? Much more work for the developer but would allow you to use all of your generators, engines and wiring in every mod in a seamless fashion.