...Indeed, it's very difficult to tell why that oddly shaped bow exists in the first place!
Backstage books say something about it being a detachable warhead, something you can ram into the bowels of a Borg Cube the way primitive submarines rammed "torpedoes" (simple immobile explosive charges) into enemy warships, and then detonate. And indeed the big bow lump looks capable of separating from the rest of the ship somehow. *
What if the purpose isn't to penetrate and explode, but to penetrate and disgorge boarding parties? Those have proven to be Starfleet's deadliest weapon against Borg Cubes in various TNG and VOY episodes, after all. The bow section then might feature prominent boarding tubes, cleverly hidden behind armored panels just like everything else on that ship.
See the two beige'ish oblong features side by side on the top surface? Now imagine those being the covers for the boarding tubes, hinged either from the forward or the aft end and thus swinging either up or down to become perfectly horizontal and to allow the tubes to telescope out and contact the enemy hull. In regular dockings with DS9, only one of the tubes would extend, and of course would not activate its phaser cutters and cast rhodinium ripping claws...
That would match what we see in the (lamentably in many ways faulty) cutaway drawing or Master Systems Display on the bridge. Namely, this one:
The ribbed area at the very front of the middle deck is indeed labeled "FWD DOCKING AIRLOCK", even though the lettering is illegible on screen and almost illegible in the DS9 Tech Manual. The idea that there would be two of those side by side is dictated by there being two of those cover plates, plus an obstructing centerline feature.
* Which is because when this ship was first designed, she was supposed to be much smaller, and the bow was a separable bridge while the two cheek things that currently launch q-torps were lifeboats. But crew evacuation has ceased to be a plausible explanation for these features, and we have seen actual lifeboats and onboard shuttles used instead.