Splitting the popup timer from the live update timer

I think this is a feature request, though it may just that I don't understand how to achieve my goal here.

I would like to disable the automatic popping up of the completions list entirely, so I can request it always intentionally with C-l. But I would also like the completions to update live, with a small (0.3 is good for that) delay.

I can't currently see a way to do that. If there were two timers, one might set the first to a very large number, or disable it completely without impacting the live updates for an active completion buffer. Is there a way? If not, are you tempted?

Failing that, would you accept a PR for such a change, should I get my act together?