To illustrate this (if but "for entertainment purposes only"The limitation on boosters is the same as on non-fill-in translators: the contour of the booster can't extend past the protected contour of the primary signal. So you still can't do anything useful that would go northeast of Beachwood.
The other problem with boosters over flat terrain is self-interference. The booster has to be very carefully designed and situated to minimize interfering with the main signal. There's enough 107.3 signal on the near east side to make that a big challenge.

Even with the boosters, there still exists a gap with city-grade 60 dBu coverage for WKSU in a decent portion of western Lake County, as their repeater map shows (blue are the full-power satellites, the two wine dots are the Ashland and Mansfield translators).

