I would suggest that the leader can then move his free foot without moving his upper body and expect the follower to mirror this, without looking at his foot. When the leader has placed his foot in the desired position he will then move his weight onto the foot and follower will do the same.
While I think it's beneficial for a follower to know where the leader's feet are, that's only because it lets her be aware of what the couple is doing as a whole and have a greater appreciation for the dance she's half responsible for producing. What you are talking about is... well, let's just say it's not the way people lead and follow in tango!
The lead for this movement (i.e. the follower sticking her free leg out) is a tiny impulse in the direction the leader wants her to place her foot, without him taking a step and doing a weight transfer. As soon as he's sent this impulse, he can then move his own free leg/foot however he chooses (in the same direction or any other). If executed properly, this creates the illusion of simultaneity. This is the same fundamental technique used in walking, just broken down into its constituent parts.
Everything is felt through your partner's body. As a leader, I feel my partner's feet through her body, just as she feels the lead through mine. Good dancing has nothing at all to do with sight and little to do with pushing: it's about signal transduction, plain and simple.It seems to me that your method requires the follower to look at the leaders chest or be behind the leader or be pushed by the leader and whatever the case, cause the follower to snatch her step.
For instance: he creates a larger impulse so that she places her foot farther (sinking down slightly makes this message even clearer). Then he takes a shorter step than the one he led her to take. That's one way... there are many others.I would also suggest that you have not answered how the leader can end up in an offset position to the follower.