You know, we might be able to get Coruscant into ROTJ if we leave the emperor's throne room on the DSII, and make Endor the sanctuary moon of Coruscant. Think about it, this would be the second time that Sidious, in orbit above Coruscant, in the middle of a battle, played an perspective apprentice against his number 1 sith.

The rebel briefing will need some tweaking though:

I think we should convey that the DSII has moved to Endor, the moon of Coruscant, for the final phase of its construction. This makes it more believable that the rebels just found out about it.

Cut the mention of the bothans.

We also need to convey that the rebels realize this is a risk, but the imperial fleet is beleived to be engaged elsewhere.

We will need to maybe redub Admiral Ackbar to give a little extra exposition that the rebels are going to Endor, the forest moon of Coruscant.

Ultimately, I think this is Commander Courage's call, since he knows what resources are available to us.