Many of the cost savings made under him were no brainers such as ending the practice of operating A330's on domestic sectors, and from SNN to JFK and BOS in the depths of winter. The more recent practice of increasing yield rather than passenger growth might work but could be counter productive if the differential between EI and FR becomes too high.
They are fortunate that Ryanair seem to have also moved away from
the very low fare strategy of the 2006/9 years. A reversal to the fly for free seat sales won't be long putting pressure on EI yields.