Keep in mind I'm not a mapper. More of an analyst I suppose.

how do you think Worker Pairing (or lack thereof) affects harass on multi-base mid-to lategame scenarios, specially on the case of BW vs SC2?

Moving away from what it changes in the game and talking strictly about how many workers can efficiently mine per base, I think worker paring is a big contributor to our harassment problem, especially on maps like Orbital Shipyard that are just begging for harassment that isn't up-front such as drops. I also think that the 12 worker fast depletion LotV has is a whopper bandaid that just so happens to not totally suck. cough mothership core cough

Also 2nd play question, what are your thoughts regarding C styled layouts for Main-Nat-Third bases on rotationally symmetric 2 player maps?

I think up until you actually claim the third base it can be difficult and dangerous to move on from two depending on the map. There are so many directions and ways a drop or harassment can enter your base while the majority of your army is making sure you don't lose your third the minute it goes down.

A map like Echo doesn't seem to suffer from this as much as other maps of similar style, but maps like Catallena can be a huge pain. It looks as though these creators go for enabling options instead of "You HAVE to take THIS base or you're retarded" which is nice on paper but frustrating to play with or against.

Dead space and far thirds/fourths promote drop play which is common in both games but almost like a wrist vein in StarCraft II. Engagements tend to not happen until maxouts because it's a lot more cost efficient to drop or warp into your opponent's base. It's less likely to get shot down, more likely to do damage, and much closer to the mineral line which is the heart of your opponent.