notify with payload (pgkill, notify)

Is the intent to replace most uses of (pg)kill with a general
purpose messaging system between the processes, or
(just) to address notify per se?

(Presumably with 'fire-and-forget' and also rpc
semantics?  And pub-sub? And some sort of
write to an fd protected by an atomic flag to
elide multiple writes when the process hasn't woken
and acknowledged the ATTN yet?)

If pgkill is not used for signalling, could this reduce the reliance on 
signals
(except for trying to kill off processes) to the point
where ot becomes much less scary to link to libraries
that use signals themselves and/or threaded runtimes?