Without the Str/Con boost, this would be fine as part of a Background. As a feat, though? Horrible.
Along with my houserule to allow the grapple attempt to be replaced with a push or trip attempt, I think I'll make the improv weapon damage Brutal 1, with the weapon breaking on max damage.
Now making the improv weapon brutal strikes me as quite clever. It ups the average damage of using an improv weapon without increasing the max. Solves some of the problems with making the weapon 1d6. And I really like the breaking on max damage-- though I think I'll make that a DM situational thing (like the iron mug probably won't break).
AD