Yes, I am already doing this in my forms (You can find my response inside that thread as well). However, There is a critical understanding missing here.
By this way, I will get the form version value only when the user successfully submits some data from the field. If, for some reason, he does not send the data (perhaps using some older version of the form), I will not be knowing his problem, specifically that he is on the old version of the form.
My suggested feature is that, Central should keep track of which user has NOT downloaded the latest form version (or in other words, which user is on which version of the form). This list should appear somewhere in the form management actions, so that it is explicitly available for action. The action might be outside ODK eco-system (like, I know that the user is offline, else his app would have received the update automatically! So I would probably try to call him, or try to reach him through some other means, to instruct him to bring his phone online and let the form versions update themselves).