Is there measurement that correlates with cohesive/pinpoint imaging?

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

Look at active speakers using DSP like Kii and Dutch and Dutch as well as studio monitors. 

I had a pair of Snell back in the day.... and Thiel, ESL63, Vandersteen..... I still have them, except....for the Snell. I certainly recognize the genius of Peter and they were quite good....

a curved baffle helps but I don’t think it’s SOTA any more....

I'm afraid all the components in the Snell A/III are outclasssed today, but for imaging and impact, amazing.  The SF Stradivari are much newer and deal with the diffraction issue very differently than a large box does.  Outstanding.