In the original series, the character Ashur was killed by Naevia on Mount Vesuvius prior to Spartacus' victory over Glaber. In order for this story to be told, at least one of three things must occur. (1) Ashur helps ensure Spartacus' defeat and is rewarded with Batiatus' Ludus as he'd envisioned. (2) Ashur kills Naevia in their dual but is allowed to leave with his life only to later escape from Glaber in the confusion of his losing battle. (3) Ashur turns on Glaber before Lucretia betrays him and leaves Vesuvius with his men.
It is unknown whether or not Lucretia will factor into this "What if" story-line since Ashur had originally intended to force her into marriage.
From among the Gladiators of the house of Batiatus, Ashur was one of two men who would have been well-suited as a Lanista. His cunning and understanding of the business side (both legitimate and underhanded) would have served him well. The only other Gladiator fit for the title would have been Oenamaeus who served under both Batiatus masters and learned the business as both Gladiator and Doctore; with the latter giving him a much better understanding of running the ludus.