Does singing from memory mean a smaller repertoire?
When I call dances at club I use a card, but practise with the music so that (after the walk through) I don't usually need the card. I have a wide selection which I'm always adding to. Calling for barn dances I don't use cards, but there are lots of dances that might go well, that I don't use, I just stick to the same tried and trusty few.

The suggestion that you should spend the previous verse of a song imagining mnemonics (3 long steps) for the next verse, seems more distracting than a crib sheet.