Removal and high capacity Silicon carbon battery?

Choose one. Fairphone does the former and is expensive for a reason.

It works if you say Ok Google. But, if you need a custom keyword. You would need to use an automation app like Tasker, Automate, Macrodroid and invoke Gemini.

As for bluetooth I don’t have an always on bluetooth speaker so cannot comment on that.

If its a convenience thing. PI with shizuku can do background(in the notification) installs. So, you can tap install on multiple apks at the same time.

It also supports RCS which would work by default for most people. The rest of the world may use something like WhatsApp or Telegram.

You can bypass the limitation assuming its not a hardware compatibility issue. Download shizuku and PI(package installer). Setup shizuku with wireless adb and you use PI to install the apk file.

I use this method to install old apks which are blocked by the OS because they use an older SDK and target older android versions.

You could try to turn off battery optimization for sherpa TTS. Maybe, that could fix the delayed start issue. But, android should’ve automatically started and kept it in memory for you.

Try SayIt. Maybe, that can work for you?