We got Jason in L.A. Thursday -- and our photog asked him if a recent reunion with Christine and other cast members is a sure sign she's gearing up to make a 'Sunset' comeback.

Jason tells us he would welcome Christine back with open arms and has no hard feelings ... but explains it's not his decision, rattling off the list of folks who would have to sign off on such a big move.

Christine was a fan favorite on 'SS' for years ... but after season 5 she left the show behind. Interestingly, some have said "Selling Sunset" hasn't really been the same since she bounced.

There's also been speculation Christine wants back in  ... this after she popped up recently at a promo event with Nicole Young, Mary Fitzgerald and Jason.

For her part, Christine hasn't explicitly said she's coming back to the show ... and she last addressed the topic in November, when she told a fan on social media ... "Sorry babe! Moved on to better things & sooo much happier."

Fact is, Christine's got a lot going on in her personal life ... she's going through a divorce and her estranged husband has been charged over alleged domestic violence incidents.