Brushless motor starter box.
 

I had the idea for a long time from a time that several of the simple 540 motors of my Serpent box did burn. Now for many years I have so called rebuild able 23T motors which are very powerful and now for a few years are on a 2nd set of brushes.
The Idea of using an ESC with a servo tester is a simple but expensive idea although a simple Asian 40A airplane ESC does not have to cost that much.

Then I saw this:
https://www.banggood.com/DC-12V-36V-...r_warehouse=UK

20A does not sound much but a stock 540 motor is also just 100W max and probably you can replace the onboard FET's for better ones or stack a 2nd on each.

Just an idea but for the money and if you have an old 13.5 or 17.T motor a worth to try.