Best move he could do was destroy the spice at the end of book one. It wouldn’t even necessary killed him and Fremen, they could save enough to sustain the addiction for decades and the next generation of Fremen would grow clean of it (spice addiction was not genetic), though to be fair someone would probably nuked Arrakis after this out of sheer spite. But destroying the spice would also destroy all the parasites of humanity: Guild, CHOAM, Empire itself, most of nobility, the transhumanist sects. Most of population was living in the feudal subsistence anyway and didn’t had any contacts with other worlds, so they wouldn’t be affected. Muad’dib Jihad, Golden Path, hunger and scattering would not happen, most importantly the final enemies would also not come, Honored Matress would not happily nuke their way through galaxy (since as you probably noticed Golden Path was a way to avoid the consequences of the Golden Path itself).
Eventually humanity of the shattered empire would again turned to the pre-Holtzmann FTL methods or invent navigational computer (and i bet it would take shorter time than millenia of Leto II rule), and galaxy would be alive again, but without magical opium fucking everything and secret superhuman cabals. Renewed reliance on technology could even break the Butlerian Jihad tenets which were the reason of the fucked up Empire dystopia in the first place.
Best move he could do was destroy the spice at the end of book one. It wouldn’t even necessary killed him and Fremen, they could save enough to sustain the addiction for decades and the next generation of Fremen would grow clean of it (spice addiction was not genetic), though to be fair someone would probably nuked Arrakis after this out of sheer spite. But destroying the spice would also destroy all the parasites of humanity: Guild, CHOAM, Empire itself, most of nobility, the transhumanist sects. Most of population was living in the feudal subsistence anyway and didn’t had any contacts with other worlds, so they wouldn’t be affected. Muad’dib Jihad, Golden Path, hunger and scattering would not happen, most importantly the final enemies would also not come, Honored Matress would not happily nuke their way through galaxy (since as you probably noticed Golden Path was a way to avoid the consequences of the Golden Path itself).
Eventually humanity of the shattered empire would again turned to the pre-Holtzmann FTL methods or invent navigational computer (and i bet it would take shorter time than millenia of Leto II rule), and galaxy would be alive again, but without magical opium fucking everything and secret superhuman cabals. Renewed reliance on technology could even break the Butlerian Jihad tenets which were the reason of the fucked up Empire dystopia in the first place.