Here's the answer before you ask.
external cap banks ADD capacitance to your ESC.
When adding a cap bank, DO NOT remove existing esc caps ( replace dead ones with new ones, sure.. rated same )
Just delivered my desk... a new HV ESC where the owner had removed all onboard caps and replaced with an external cap bank.
I know this fellow had the best intentions, so there will be no finger pointing and gesticulating (look it up) for all to see.