2nd Hand Man's page

Agreed. With the +1 to AC and +1 to hit, the only reason larger creatures have a mechanical advantage is weapon sizes, and it simply makes no sense to set a small longsword at the same damage as a full-sized one. Child-sized weapons have been made, and the effective difference has been evident.

The only place where I consider the size modification to be blatantly wrong is with a firearm. The only reason why a firearm would become less powerful by scaling the same weapon down, is if you were to change the powder count. With Firearms, this isn't necessary, as all you would need to do in order for a smaller person to use it is to shorten the barrel and/or stock. The resulting shortness of the barrel, however, would definitely amount to a loss of accuracy.

Then again, Pathfinder really hasn't managed to get firearms right yet.

You could always dip a level of Witch and get prehensile hair, and simply use your beard to reload. That would at least handle the lack of limbs issue. Otherwise, I think others have given good advice so far.

It will be rough early on when that -2 is a significant difference to your attack score, but so long as you have a decent strength score, the difference in size will be a benefit to you.

I would personally say go for it. Samurai gets full BAB, so this wouldn't be much harm to you in the long run. Consider that you aren't simply increasing the damage by 1d, you're also using the weapon two handed. That changes the Katana from being 1d6+Str to 1d8+1.5*Str. Just watch yourself at low levels and you'll be fine.