I know it might be little costly but I know it will attract crowd to Nokia with out much hassle.
Feature should be included down from Nokia 5 (2019 ) to Nokia's upcoming flagships.
ESS sabre or Wolfson DACs are best in industry .
We want ESS tech headphone amp (since it is small and cheap) or other headphone amp capable of driving high impedance headphones .
Dual stereo speakers should be included at bottom . Speakers should be best in class.
Last of all Nokia should have good audio processor to improve surround sound effects.
Wishing the best of luck.