You have an extensive catalog of music. I can see why control is important to skip, replay, pause etc.
So, the real question is do you want to connect to your device to access your library and possibly somewhat improved sound quality or to have the ability to control your device?

I don't think BRP will be updating anything specifically to your interests any time soon unless there is reasonable demand and $ to me made. As others have already noted, BRP Connect/Go has been a sore spot for many. Trying to connect devices and utilize that package can be quite aggravating, but bluetooth does work without using the app or cable.
I connected my phone via the cable and app when I first tried using it b/c that is how things are described to connect. However, that was very short lived. I never connect the cable or launch the app to connect to phone anymore.

Even though you don't want to take this route, connecting your phone is probably the most viable option for what you want. You can always copy some of your music to a SD card and install it on your phone. Then, play over bluetooth. If you concern is that you don't want to deal with calls and texts while riding, turn on your do not disturb feature.

I'm not sure about this high end mp3 player that you referenced, but high end doesn't mean it will work with everything. Some things are proprietary and that in and of itself can be a problem.

Any way, I hope you find a solution or reasonable compromise for your music needs. I'd guess you're not the only 1 looking to solve this. It's just a matter of time before it happens.