On both Hirschfelden and Layton, there remain missions that contain fragments of a time where the .270 was ethical to use on coyotes, foxes, and roe deer. This has not been true for some time now, and thus there is a guaranteed-failed harvest check waiting for anyone who does those missions.
My suggestion is: have "The Great Coyote Tour" require the .243 instead of the .270
"The Fox and the Scope" to require usage of the Argus scope on any rifle (or if that's beyond coding possibility, any scoped rifle)
and for Sommer #6 to require the .243 instead of the .270 as well.