Like carve out a place between Russia, Belarus and Ukraine in the former Pale of Settlement. Establish a bunch of Yiddish language schools there. Have it become a center of Jewish culture. Sure, there are already Ukrainians, Russians and Belorussians there but there were already people in the far east too.
The settlement of The eastern frontier was always paramount. The JAO was an extremely underpopulated area right on the borders of China and where many royalist a had run to before. Not the right time or right place to designate for survivors of genocide nonetheless.
However, if Bessarabia and Odessa had been designated for the already considerable Jewish populations, in tandem with the deportations of multi-national populations derived from Catherine’s colonization efforts (inviting Scandinavians, Germans, Greeks, Poles, etc to displace Tatars), I think it would have been more successful. Odessa was one of the most Jewish metropolises in the world alongside New York, and only when they could in the 80s did they leave Ukraine for Israel or the US, largely because of economic stagnation and the weird anti-Semitic messaging Brezhnev seemed to be propping up when pushing against Ukrainian nationalists.