The best way to add them- or count them somehow- would have some kind of system where it expreses the value of a pitcher's offensive production in their defensive stats (era whip etc) that are counted. So, for example, some thing like: Livan gets a walk, you subtract a walk, if he gets a hit, you subtract a hit, if he gets an RBI, you subtract an earned run, if he hits a HR you subtract a HR allowed etc. (though if he hit's a homerun he should get an extra win, imho)
It's not entirely accurate, but it would be cool to count the stats somehow. It would only work in NL only leagues. It's simply not fair to do something so league specific in a mixed league.