Plenty of people have suggested that a ‘separate incarnation or a second sacrifice of Christ’ would be necessary, or desirable. The universe might be full of Jesus-analogs, administering to crab-people, spider-people, octopoids, bee-hives, and so on, as Olaf Stapledon suggested (I quoted his ideas a short while ago, in this post A question about Christian religions that believe a Rapture is coming - #33 by eburacum45 )
Indeed this may even be true in the real universe; the fact that some, many or most intelligent aliens have some sort of Jesus-analog in their past does not imply or require that salvation is a real phenomenon.