Werebears are supposedly a major problem in Skyrim, hence their absence is something many people want rectified. Even if you just had people telling stories in taverns about them, and never encountered them, it'd be a nice change.
For me I don't need a special guild for werebears or even a questline with them, honestly just having them patched into the wild is all I need since that follows the lore. And of course the ability to catch the disease from them. Bethesda could easily incorporate this, if they made werebears slightly stronger than werewolves, have an armor rating, and some other differences than werebears would be perfect. Adding them wouldn't affect the Companions either because Bethesda could just make it so that if you join the Companions and drink the blood then it gets rid of your werebear strain and adds the Companions strain since you could look at it as their strain being from magical origin rather than contracting the disease, so it takes over and gets rid of anything else.