Is there measurement that correlates with cohesive/pinpoint imaging?

Well, that's unfortunate!  Lots of speaker companies claim to have a focus on coherent imaging, but nobody has any idea how to measure it?  Do phase alignment/time alignment correlate?

Lots of speaker companies claim to have a focus on coherent imaging, but nobody has any idea how to measure it?

it is measured by frequency response tests

Hey OP:

You really should at least start to read about HRTF. It will help you see the problem of imaging in a whole new light, and why it is so hard to measure.

  Do phase alignment/time alignment correlate?

Not in my experience, but clearly the fans of speaker brands like Thiel and Vandersteen feel strongly they offer special features you cannot achieve otherwise.  Personally I vote with the literature, that says we aren't that sensitive to phase or time alignment. We _are_ sensitive to badly matched drivers however.

There's also some research saying that making the frequency response dip around 2.4 kHz enhances the experience with the trad off being a neutral frequency response.

It is also important to include the room in these discussions. Not only does controlling reflections matter but enhancing diffusion in areas also helps a great deal.  I find that imaging is enhanced in the same plane as the room treatment.  Want wider?  Treat the sides.  Want taller?  Treat the ceiling.  Want depth? Treat behind the speaker and behind the listener.

The best speaker in the world can be ruined by a poor room.  Conversely, some speakers reduce the interaction with the room, like line sources, planars, horns and open baffle.

Time and Phase. Study how the highly evolved ear brain function to localize food and threat sounds and you will understand it is small timing differences. Add in low diffraction because a large baffle destroys time information while functioning as a mechanical averaging machine ( frequency response )
read what JA has to say about Vandersteen “imaging champs”.... 
I will say if your references are studio multi track efforts you might be leaving a bit on the table relative to expectations, especially image depth

enjoy your speakers ! And the music

because a large baffle destroys time information while functioning as a mechanical averaging machine

Wait, what? Some of the best sounding, best imaging speakers I've ever heard are the Sonus Faber Stradivari and Snell A/IIIs. 

You can make a wide baffle with low diffraction, and if you can go for it. :)

Best,

E