CO will book stopover not in hubs, it just takes the right rep.
I just booked EWR-HNL-LIH- (open jaw) -OGG-LAX-LAS (stopover)-EWR using CO miles.
Bizarrely 2 agents had a problem booking a UA flight from OGG-LAX so I booked the CO flight. After it was ticketed I successfully switched it to the UA flight.
you arent backtracking OGG-LAX-LAS-EWR is a straight shot while EWR-MXP-FRA-TLV-VIE-PRG-ZRH-EWR isnt (thats where MXP & PRG are the stops and TLV is the destination)
now I know DL used to allow stopovers on free Domestic tkts but only at their Hubs, didnt know CO allowed it anywhere, not that I cash in for Domestic tkts that often.
As for Hawaii not worth it to me to use miles when so many EQMs are at stake. My HNL flight on Sun returning Weds will earn me 10,400 EQMs , used 2 CR1s on UA and was UPed on 4 of my 5 flights the last 1 IAD-JFK is a CRJ200 only Y. So for $162 out of pocket (used a $600 CS cert) Im flying Biz and FC to/from HNL and earning 10,500 EQMs and 21000 RDMs, who say it doesnt pay to buy tkts
And the Biz seats on the UA 757p.s. flights are plenty good, although CO has better IFE and food
but back to BA & AA