Four shoulder buttons and a physical volume wheel should be more than enough for music playback control. No need for extra buttons. The only somewhat annoying thing is that the audio jack, volume wheel and shoulder buttons are on the long sides, while it would be better to have them together at one of the short sides so you can easily keep the device in your pocket. But there's no way to avoid that problem.
I still think having speakers at the outside (on the short sides of the base) would be useful: when you're listening to music on the go without headphones, when you use your Pyra to set an alarm or to get any kind of notifications, when using it as a phone, and so on. Yes, the direction of such speakers would not be optimal when using it as a handheld. But it would not be that bad either, and the stereo separation might even be better. When you want good quality sound, you'll use headphones or external speakers anyway.
I still think having speakers at the outside (on the short sides of the base) would be useful: when you're listening to music on the go without headphones, when you use your Pyra to set an alarm or to get any kind of notifications, when using it as a phone, and so on. Yes, the direction of such speakers would not be optimal when using it as a handheld. But it would not be that bad either, and the stereo separation might even be better. When you want good quality sound, you'll use headphones or external speakers anyway.