As far as I know, want, need and mean can be used in future progressive or perfect progressive only.
in polite enquiries: Will you be wanting a taxi tomorrow, sir?
in polite requests: I will be wanting a taxi at 5 o'clock in the morning. (it's not that I really want, I need it)
I am not sure how we use them in perfect progressive. Anyway, the use of these words in these tenses even if legitimate doesn't seem to be very common.