This is just my personal opinion and it's driven by what I would afford for such a kitchen/dock layout...

I would pour a slab at the bank for a kitchen/picnic shelter and then add the dock nearby for swimming. This would keep expenses to a minimum for any electric and sink drains AND would give some separation of the cooking/picnicking activities from the swimming/horseplay.

This sounds like something I could do myself and save more money.

I do like the idea of "out in the middle", but I imagine that would require post sunk into the bed of the pond or concrete piers. I would still envision wood decking...the whole elevated concrete pouring thing would have to be left to those more experienced.

Fish on!,
Noel