I think I first requested the "segue/radio" type crossfade a good 10 years ago when i first purchased Poweramp. In fact, so long ago that the post doesn't exist any more! 😏
An option to change "fade in" and "fade out" separately.
A natural fade out with the option to start the next song at full volume.
I too remember the sqrsoft add-on in Winamp and used it always.
This appears to be a popular and recurring request, so I'm surprised the tech team have never seemed to address it in at least 10 years?