I'm glad you're enjoying ESC development; it's very satisfying when they finally stop producing smoke and start behaving properly :P
With regards to building a lifter, you want all the weight as far back as you can so it won't fall forwards instead of lifting the other robot. The scoops will help keep the pivot point forwards, but worth baring in mind. If you want to go brushless, I have some blank VESC PCBs if you want to try putting some intelligent controllers together (google VESCs for more info). Would mean you could use some really small brushless and still get plenty of power out of them.