On both Futaba and JR servos, the "hot" wire is in the center so if you put the plug in backwards, the hot wire is still connected to the correct terminal, only the signal and ground are interchanged which does no damage. The servo just doesn't do anything. It's Airtronic servos that you have to be carful with. They insist on haveing the hot (+) wire on an outside terminal. These have to be rewired before using them on a Futaba or JR RX. High Tech and most others use the JR system.

As far as battery connectors are concerned, I personally have standardized on Dean's Ultra Plugs on all my e-planes, even though they are overkill for park flyers. That way one charger can handle everything. I think they are good for up to about 100 amps.