They may be endemic outer-totalistically, but we're thinking in terms of non-totalistic transitions, and anyway, I don't think alternating rules count as rules in the isotropic non-totalistic rulespace, and this project is only considering that rulespace (at least for now). Regardless, any posts here won't make a difference; this would presumably be a separate site or application, with no direct connection to the ConwayLife forums.
Also, other achievement suggestions:
"In Reverse": find a non-monotonic spaceship.
"Backing Up": find a non-monotonic spaceship with a period of ten or greater.
"Knight": Find a knightship.
"Camel": Find a camelship.
"Giraffe": Find a giraffeship.
"Ibis": Find an ibisship.
"Flamingo": Find a flamingoship.
"Zebra": Find a zebraship.
"Antelope": Find an antelopeship.
"Safari": Find at least one of each of the above ships.
"Sloth": Find a knightship, camelship, giraffeship, ibisship, flamingoship, zebraship, or antelopeship with Euclidean speed slower than c/10.
"Snail": Find a knightship, camelship, giraffeship, ibisship, flamingoship, zebraship, or antelopeship with Euclidean speed slower than c/20.
"Martian:" Find an oblique ship that's not needed for the Safari achievement.
In general, I think we should try to have a good mix of "boring" achievements (ex: find a _____ with no conditions) and more interesting achievements (ex: In Reverse, Sloth, Snail). We could also have some hidden achievements, which are more joke-y and sometimes outrageously difficult to get. If we do that, here are some ideas:
"Funny Number": Find a spaceship with period 69.
"How Did You Know?" Find a spaceship with a period equal to the last number of your IP address.
I'm open to suggestion about removing, modifying, or changing names of any of these achievements -- these are just suggestions.