You could actually do an interstellar Gundam series with aliens and keep true to the original Gundam ethos....

Okay, I get that a Gundam series with an interstellar setting and aliens would be just be seen as Macross with the serial numbers filed off. But it can be kept true to the original Gundam ethos of the horrors of war even with aliens and an interstellar setting since well, if we expand beyond the stars, we'll just bring our problems along rather than outgrowing them. And the same could be expected for other species as well. Don't expect that first contact with other life would go smoothly even if we have something in common, especially if that something is problems that we share such as war and greed.