Charger... had great luck with my fake b6 charger from amazon for $25-30. I use traxxas connectors with alligator clips to charge
(i solder them to all my cars).
I don't really understand the question about changing connectors on the car.
What I'm saying is that redcat racing uses 4mm banana plug from battery to esc.
I can find 2s lipos with the stock plug. same as the two nimh I already have. Can't find a charger with the right plug. Thinking about possibly changing all connections to common ones like deans or traxxas.
What I would do is cut the Redcat connector off the stock battery. Solder a Traxxas connector to it, Now plug that into the Redcat ESC. Buy spare Traxxas connectors for your batteries and solder them on. Now if you fry an ESC, they won't deny it because you altered the factory wiring.
Also, I know I'm gonna get jumped for saying this but if you want to keep it cheap just stick with a nihm battery. I run 8.4v nihms in my son's Caldera and it fly's with the extra cell. You won't need a balancing charger or balancing plugs or any of that other crap. I know Lipo is the battery of choice, and I realize they are better for the highest speeds, but you can pick up a racers edge 8.4v nihm 3300 mah for around $32 and use any old charger you want. There will also be a very noticible difference in speed, and you won't have to reprogram anything on your ESC, just plug and play.