The problem with the Jags is the stadium. The Bears need to sign off on it. I could see that happening, via waving the 80 mil penalty, plus the NFL pressuring them and using the money they give to the Bears for the stadium as an incentive.
But what about the stadium? If the Bears are already building a potential dome or retractable dome, there's no way throwing a dome over or around Soldier Field can compete with that. The location is terrible compared to Arlington Heights, plus the facility will surely have a lower capacity. You might actually find the Jags wanting to share the new Bears stadium before playing in a revamped Soldier Field.