I know that game launchers can be controversial, but hear me out.
I envision an SL game launcher that offers a similar functionality like the Blizzard bnet client.
The launcher has the following features:
  • Messenger client: you can chat your with friends. Clicking TP-offers automatically launch the viewer if not active.
  • News page: you see general SL news as well as upcoming events. Clicking event links automatically launch the viewer if not active.
  • Button to launch the viewer
SL by default does not open the Viewer directly but starts the launcher (you will still able to open the viewer standalone.) The launcher by default automatically starts with Windows. The launcher consumes only little system resources and by default hides in the system tray when closed. It therefore offers an "always-on" presence. Your online status shows a special flag when you're only online in the launcher.
Why do I think that this would be anything special?
I came to this idea when I heard people talking about how they can reliably reach people outside of the viewer. Some SL users are on discord but only a fraction. Some are on Primfeed but only a fraction. Neither really connects SL residents outside of SL, and neither will in the future. An "always-on" launcher would solve this issue. Even if your viewer is closed you are still connected to your SL friends if you want.
It would increase engagement between users because it's easier to communicate (the limitation that both need to be on in the viewer at the same time is gone) and it could also increase the engagement of the user with the platform if the news/event content shown in the launcher is interesting and relevant enough.
Essentially the launcher would be optional but enabled by default, and act like existing game launchers that people are used to.