As I understand mind-mapping it's just a method of gathering ideas on a page, using words, pictures, diagrams and colours. In a sense it's just a mnemonic system that can facilitate learning. Ethics don't come into it; if it works for you, use it.
But chess for nursing board exams? It's never gonna work. I can play a pawn fork or a discovered check with the best of 'em but anything more complicated than a band aid is beyond me.
Honestly, Fitz, ANY method you use to enhance your memory is just fine.