Jazz mixes like this are rule-breakers. You don't have to have the bass in the centre, especially if the bassist takes solos on some tracks. However, I would tend to centre the drum kit (at least the kick) and make the OHs a little wider than you might in a rock band mix. That leaves the piano, and I think I would bring the treble side about half-left with the bass end spreading not much past the centre. The bassist could then be in the right half of the space, but with the room to occupy virtually the whole of the right half if that felt right.

The important point in mixing jazz of this sort is frugality. I don't know, for example, how many tracks were recorded for the drum kit, but I would see if in the mix I could get away with using just kick + overheads, and certainly not go beyond adding a little of the snare track.

You could also make reverb do some of the positional work for you. Because of the isolated and dry recording, you will need a good reverb for this, applied separately to each track. Drop a PM to Chris (audiokid) and see whether he could put a part of a track through his Bricasti to get an idea of what that could do for you.

There's also quite a bit of creative miking technique to those types of recordings... arrays like M-S are often used to capture the ensemble as a whole instead of direct miking individual instruments alone.

Now, for your situation, in that you are dealing with tracks that are already recorded - for better or worse, hopefully better - I agree with Bos in that you don't have to approach this as you would a rock or pop mix.

Letting those instruments breathe within their own space - as well as in connection to each other - is going to be key in terms of reproducing that "classic" sound you referred to.

Listen to, and reference, vintage tracks by cats like Brubeck or Kenton, and you'll hear a lot of space. You certainly don't need to approach this mix with the standard go-to settings of the kick and bass in the center.
In fact, you'd probably be better off to not do so.

It may also help to ask the players where they normally set up positionally when they play live, and in this case, don't be afraid to ask them for their input on panning and positioning of not only the direct tracks, but of artificially added ambiance as well.... and don't be afraid to run a completely dry mix of this the first pass through to get an indication of the relationship(s) between the instruments. Bos is right... in this case, less is more. You don't want this to end up sounding all washed out with a huge amount of verb.

And finally, her's one more trick I would try, just for fun...

get your basic mix happening, set your pans to taste...

Now, run that mix through a stereo PA, and then M-S mic the PA system ...and bus it back to your DAW.

(And, don't forget to flip the phase on one of the figure 8 tracks upon playback of the recorded PA tracks..) ;)

The M-S array just might get you some of the space and imaging you are looking for...

If you're not experienced with M-S mic technique, let us know and one of us can walk you through it. :)

FWIW
-d.

Check out some recordings of The Bad Plus for a modern trio with the same instrumentation. As suggested above - drums center, bass and piano to either side. Another personal point - it's a trio - for me it doesn't need the spread of a big band or orchestra.

Many thanks for your replies and tips!