[The Listener]

If you record each instrument stereo you don't have to (mustn't) pan each stereo pair extremely L-R... you pan with taste (try also in mono - for phase and also you can hear the position where the panning sits well in the mix...). You can send the stereo pairs to subgroups and pan the compete stereo picture of individual instruments... You treat those close stereo recordings as you would treat mono instruments... don't spread everything over the whole picture...

Figure 8 would catch a lot of bleed only if it is pointed towards the bass, but if its def point is pointed towards bass it would actually catch very little of it... You shouldn't care too much about the bleed - position the players as much apart as you can and that they still feel comfortable - position mics carefully... that's all. Actually in the position you mentioned they can stand in a slight "U" formation and the figure8 def point can be directed directly to the bass and M mic facing completely away from it...

If it is 2 NT5's - use one pair fot ambient - but still - in this case maybe if you want a very high-end ambient recording use plan B - Sennheiser MS pair for ambient, Schoeps for piano stereo, one 414 for sax spot micing and another 414 for double bass spot micing... and leave NT5's out of the game...
In the mix you pan according to the ambient recording with some liberty preserved (when it sounds good, it sounds good...).... Probably EQing spot mics to combine well with the ambient pair - maybe removing some picking noise and exaggerated mids form close micing the bass, some high shelving on close miced sax to remove harshness exaggerated air and clap noises, etc.
Maybe you will only need to add a little bit of spot mics in the mix and the main picture can come from the well positioned ambient pair...

best

P.S. post your recording when done if you can...