I've always been hesitant to stick my nose in here, since nobody's ever accused me of being a good dancer, but there was an album cover back when Bossa was popular (in the days when there was a new fad dance every week) that described the basic step as LF forward, RF closes to LF, LF replaces, with a QQS count, then the natural opposite (obviously it wasn't in exactly those terms, but you get the idea). That,very much a modified forward and back basic, plus the fact that Tom Jobim always said Bossa WAS samba, reinforces your idea. Some of the samba figures never felt appropriate to me at the slower tempo, but what the heck, it's a popular dance sans syllabus, so there's no objection to making stuff up as you go along.