Though I guess we all are to some degree, I've always been a bit of a thief, one to try to take advantage of the work others have done.
When I was first diving into college football play-by-play data (and was not yet working with Football Outsiders), I pilfered the idea of success rate and adjusted it to fit NCAA standards. And once I was having fun with that efficiency measure, I decided the best approach was to tinker with ideas for explosiveness (which eventually became PPP) to make something like an OPS for football.
Last year, when I began to realize that I didn't like the redundancy involved in PPP, I gravitated toward baseball's isolated power concept and adjusted my ratings to only look at the explosiveness of successful plays.