In ANH the Rebels had to fight, they didn't have enough time to evacuate before the Death Star blew them to bits.
In ROTJ they are told there is some time before the new Death Star is fully operational so in theory they could have waited a little longer to gather a larger fleet and plan a tighter scheme of attack but the added bonus of killing the Emperor was too good an opportunity to waste.
The Emperor being there is the reason they are doing this there and then.
Moving him to Coruscant makes no sense at all, the only thing it does is make the view out of the window look more like those in the PT and we have three films of that sort of thing to sort out already.
Nobody has ever suggested putting Palpatine on a flying saucer.
The suggestion was for him to arrive on a mobile palace which is docked with the Death Star.
It's physically linked to the place as in earlier draughts of the script for Jedi.
Ghost if you don't like a suggested idea I can live with that, not everyone will agree with everyone else and there are some ideas that people have suggested that I don't dig either but please address the actual idea and don't distort it to dismiss it.