I like both Gillibrand & Heinrich... and I originally thought Heinrich may be good on a ticket- But I have about decided that Heinrich is too lacking in the charisma dept.
I think a better ticket that includes someone who is somewhat palatable to moderates (that is younger, from the SouthWest) would be:
Castro/Sherrod Brown.
(that is assuming Castro is very visible on cable news the next 2 years... and proves to be very credible & likeable with his messaging).
Or Gillibrand/Brown.
I don't have a good enough sense yet regarding how Gillibrand would hold up as the nominee. I know her views have shifted a bit over the years (which is fine with me... but could give fodder to others).
But a primary will be good to see how such things shake out (very interested to see how Gillibrand, Castro, Heinrich, Booker, Brown, even Schatz would do in a primary campaign).... who has the right tone, message, etc for voters and how they hold up to various criticisms in 2020. I do think there is a very good chance that the VP choice will be a candidate that finishes 2nd or 3rd in the primary.