That's essentially what the prototype projects are doing, except optimized for taxiing vs. "just" pushback or maintenance moves - normal pushback truck is not e

That's essentially what the prototype projects are doing, except optimized for taxiing vs. "just" pushback or maintenance moves - normal pushback truck is not exactly prepared to handle high traffic taxiing, partially due to how communication between aircraft and pushback is handled. So those projects investigate a solution that is optimized for the whole taxi trip at full traffic at the airport, including electric solutions to avoid currently heavy diesel pushback trucks.