I carry a FiberFix as well but I have not had to replace a broken spoke since at least 2005. I build all my wheels with
DT Swiss AlpIne III spokes. They are about 50% stronger than regular double butted spoke. They are the equivalent of adding at least 4 spokes (
Ric Hjertberg says 10).
For cassette removal, I have Phil Wood FSC hubs. The whole cassette body with the cogs slides off so that I can get to the spokes if I need to. I haven’t needed to ever needed to, however, since my use of the Alpine III and the Phils kind of coincided.
If you don’t want to spend the money for Phils…
and they are pricey…, Velo Orange
sells a toolless hub for about $160 a hub.