What about building the deck closer to the pool where the ladder is? I can only imagine that the deck is built away back from the top rail. Is there maybe some way that you could add on to the existing deck, maybe cantelever some 2x4 or something towards the pool, and overlap a bit of the top rail? If I were to do it I would carriage bolt the boards to the deck and route the edges, you could even use a bit of 1" plywood for that matter I suppose, stain it to match.

I think that ultimately what you need to do is move the ladder, and making the transition any different at the bottom is not an answer to a problem. Good luck.