re:"MS should make it more prominent which KBs support hotpatching. It is an under-used feature."
It's not under-used, we don't use it (well, haven't really). Not all fixes are hot-patchable, and it takes only one hotfix/GDR to force a reboot for the whole batch in a patch Tuesday. The likelihood of being able to avoid a reboot due to hot-patching is close to zero.
[Due disclosure] I work in the team that issues hotfixes/security updates/service packs, etc.
