Broken freehub pawls typically make the wheel unridable. You'll be freewheeling in both directions. In the tips and tricks thread or some other freehub thread, someone posted a tip about using some metal wire to tie the spokes to the cassette as a limp-home mode for a failed freewheel. This would have to be a last ditch effort as you'd lose the ability to freewheel among other things.
If you are that concerned about it, look into replacement freehub options. Hopefully they didn't use some proprietary design (though they likely did) and you can replace it with something with a better track record. That said, if you aren't having problems and have used several wheelsets, I wouldn't lose sleep over the issue.