In 2001, Bombardier looked at shrinking the CRJ700 and making a replacement for 50 seat aircraft and calling it the CRJ500. They abandoned the idea after thinking that it was going to be too costly to operate compared to the CRJ200 and E145. Looks like the idea was too early for its time.
https://www.flightglobal.com/news/articles/bombardier-eyes-crj700-39shrink39-134077/