jwm is missing because microcore + core elements is now wm agnostic, ie you choose the wm you prefer and install it as an extension (there are quite a few to choose from, including of course jwm.tce{e,z}).
interface to wm is via some interface (wm_initmenu, wm_makemenu, wm_restart, wm_setbackground script interfacde), where wm is indicated in ~/.desktop.
.desktop also contains the name of the icons manager, so I may guess than in some future release, wbar might be out of the core and some mechanism will let you choose another icon manager.