Hi Dan,
that is about the way I handle it, any kit with a true Airfix pedigree is OK with me in whatever manufacturer's box or bag it may come, but I also draw the line at other's kits in Airfix boxes, I would not build those for an Airfix build.
But for a themed build other than an one-kit-build, I would welcome contributions featuring other classics such as Frog, Aurora, Revell etc. as long as they are true classics at least 40 years old (which is a little later than when I started modelling

).
Cheers,
Jens
Information not shared is information lost.
1/87er, die feinmotorisch flinke Elite des Modellbaus.
http://www.scalemodelteam.de