Steepling is not easy. Simpson is probably the one with the best combination of flat and steeple times after Chepkoech.
Eilish McColgan has run 4:01, 8:31, 14:48 and never broke 9:30 in the steeple (admittedly her flat PBs came after she quit steeple but she had 8:48 flat vs. 9:35 steeple which is quite poor, compare e.g. to Krause with 8:49 (i) and 9:11).
So you cannot simply take someone like Hassan or Obiri, train hurdles for a season and expect them to run 8:40. But some of the women who can run sub 4 and sub 8:30 flat might be able to do as well as Chepkoech.
But a woman who can run 4:01 and sub 15 will be among the top runners in most countries and has a shot at medals in many continental championships. Many may not want to change to the injury prone steeple even if they could in theory be among the top 3 in the world in that discipline. IF they learn to hurdle well, that is.