I haven't done this for a while but a few years ago when I had to travel to Asia a lot I did this all the time with no issues at all. I wouldn't even consider it to be pushing the envelope and I do not believe it would be legally permissable for BA to interfere in an individual's travel patterns.
I used to make it very clear to BA when making changes and amends what was going on with my tickets and no-one batted an eyelid. That was a while ago though so YMMV.