The only problem is remembering what is powered by which. An accurate schematic is needed for the future, because details will be forgotten.
Unless the ballast is really needed, a collection of 6 volt NiMH is better. Far easier to look after.
All ESCs that have a built in BEC draw their control power from that, as well as offering it to the red servo wire. ESCs not so equipped need to keep the red wire connection.
It is important to remember to switch everything off at close of play. I have memories of a tug with two ESCs, each with a black switch on a black background, one just out of easy view. A slowly, but thoroughly, discharging battery seemed to be the cause of lots of mystery symptoms, such as eletronic bits that should have remembered settings, forgetting them.