I would put up with the delay and have they fix the slab. When my new pool was getting done last year I had a low spot and the PB convinced me the kool-deck would solve it. It was like 1/8", no where near as large. They built it up but still puddles and I hate the puddle, attracts dirt and I really wished I would have made the PB make it drain right prior to kool deck. Also 1/2" seems like it would be too thick for kool-deck and would crack, but I am not a pool deck professional, just judging from my own kool-deck I saw done. I would also think about Acrylic, just slightly more $$ and holds up better they say to stains and cracking as compared to plain old kool-deck. I wish i would have inquired when my pool deck was done about a year ago. (new IGP)