I'm looking for various 'pitstop' positions—situations where it's relatively safe to stay and from which you can execute different passes or attacks. For example, I think HQ is a 'pitstop'.
There are many. Some of the most useful in my opinion:
Figure-4 bicep guard
2-on-1 / Russian tie
Knee shield half guard
Single-leg X
Headquarters
Body lock passing
Half guard top crossface + underhook
Gift-wrap
Technical mount
Front headlock
Seatbelt from turtle
Kimura trap
Leg drag
Saddle
Back body triangle