I should add that option a. above is rinse-and-repeat. The OS upgrade process (5.0, 5.1, and in the future 5.2, 5.3....ad infinitum) does not remove libraries, so you may keep your old packages installed as long as you like.
Granted, there are other window managers, also, if you don't like any of the options I've suggested. Gnome and KDE and XFCE are not the only ones, as
tls pointed out in response to your complaint. With a quick look through the leaves of the x11 branch just now I counted 43 of them, but I may have missed a few, and that doesn't count the two window managers that come with the OS.
