Barnabas,
I have a Beneteau 311 that has a very similar sail plan and rigging to the 323. It has a 116% jib that sheets inside the shrouds, so a larger headsail would have to go around the shrouds at a wider angle. The boat needs more sail area in light winds, but is fully powered up at 12 kn apparent upwind.
I don't have a problem with the weather helm you mention. My helm is very balanced. If I find that I need more than one spoke of helm (or 2/3) due to heeling, or I am healing more than 14 deg, I let the traveler down to leeward. I make much less leeway with less heel, especially double and singlehanded, so VMG is better. If the traveller is down most of the time, I take in a reef. Going to windward, I'll get down to 2 reefs before, I start rolling up the jib. My boat is much happier going to windward with a full jib and 1 or 2 reefs in the main. Off the wind the jib and main can be reefed together if desired.
The keel on a 311 is heavy enough, but doesn't have that much lateral area, so it slips to leeward pretty easily if heeled over. Presumably the 323 is similar.
I worked out a plan with a sailmaker that would fit a 165% jib that with the sheet lead going to the back of the inboard sail track, on the side deck, near the back of the cabin top. (It is odd that the Beneteau installed a genoa track that runs back that far.) But what I actually bought was an A1.5 asymmetrical spinnaker from Doyle, as seen in the thumbnail to the left. It is a light reaching spinnaker, 621 sq. ft, 17% bigger than the standard main and jib together, but less that maximum spinnaker size allowed by PHRF rules. It is a great sail for up to 12 kn apparent. I bought it to keep the boat moving on 4 kn days, rather than run the engine, but it has made me more competitive in distance races also. In lighter winds I can sometimes sail as high as 55 deg apparent. I can sail downwind up to 135-140 apparent, but lower than that the sail just dies and I have to head up to get moving again. Theoretically I could sail straight downwind wing and wing in drifting conditions with a whisker pole, but I seem to keep up to other boats by sailing the gybe angles.
For the readers not that familiar with the Beneteau 311 and 323, the normal sails for the 311 are a main of 277 sq. ft, and a 116% jib of 255 sq. ft, on a fractional rig (but more like a 9/10 fractional rig). So the main and jib are of similar size. These proportions can be compared to boats from a decade or two earlier that had 155% genoas to take advantage of the racing handicap rules, so that the genoa was roughly twice the size of the main.
Later I also bought a Code 0 for sailing on a close reach, 439 sq. ft. It is roughly equivalent in area to a 200% jib. This sail also helps me to keep the boat moving on light air days, but is a better sail for sailing above a reach than the Code 0.
Good luck.