Omega could pick a different color for the opaque box in the real and simulated worlds (without the agent knowing which is which), so that the real future agent can't be the successor of the simulated one...

Oh. I missed that. This would also break the similarity to Absentminded driver problem...

But no, this doesn't work, because Omega is known to always guess correctly, and there exist agents that one-box if the opaque box is red and two-box if it's blue. So, the simulation must be perfect.