As GB says piano is always a challenge, with bass next... The drums always rule the room (exceptionally sensitive drummers balance themselves effectively but when they hit points of emphasis the drums will always be the loudest thing you record), though horns can also approach drum levels (if there's a horn section that together typically becomes the loudest part of the ensemble).
Setting up close to the piano may work if it doesn't distort the perspective/phase relationships. I sort of think that would only work if the piano is center stage (which seems rare in clubs).
A spot mic leads to mixing in post but absent a PA mic on the piano and an amp for the bass that is often the only way you would get effective ambient balance.
As an example the Tyrone Allen piece on my page here: https://soundcloud.com/sounds-from-dc
was a completely ambient recording of a quartet (though an atypical quartet since he chose not to have a drummer, perhaps in part due to the acoustics of the room). The mic location can be seen in the thumbnail photo. There were no PA, no microphones and no amps (so the bass is just natural sound off the instrument). They had excellent control of dynamics but the saxes are of course much louder than the piano and bass. He's a fairly forceful player so the bass was still a bit louder than the piano (for proximity I hoped to stay close to the bass thinking it would be light, so that is also a factor). I would not have wanted to shoot from the side of the stage across the piano to try to get more since that would not have worked for the spatial representation nor with the directionality of the other instruments.