Absolutely. And I've done this (Sydney to Chicago, with stopover in Honolulu) and it is fantastic. We were on a Hawaiian 767 on the Sydney to Honolulu leg, and of the ~250 people on board, only a small handful of us went through the immigration/customs line for U.S. citizens, and the rest were in the other line...so we FLEW through. (Tourism of Australian nationals to Hawaii is actually a thing). Not to mention that Honolulu is basically directly en route from Sydney, not out of the way at all distance-wise. And it nicely breaks up the flight from a duration standpoint.
So, yes, Hawaiian air is already on that route on the other end.
Long story short, your observation is correct: a GREAT stopover (and perhaps layover) spot.
Not to mention, if you do a stopover coming from Sydney, your flight basically straddles the international date line, so you end up with this weird effect of being in the same calendar day for some very large number of hours.