I'll add two comments, but first - awesome plan! I love it.
With any young kids in the pool, yours or others, there appears to be a significant blind spot for lifeguarding in the rock nook. If that visibility issue it correct, I'd have a tough time recommending the design - though fantastic.
On the niche vs nicheless, the nicheless are obviously smaller and therefore more nimble from a design and function standpoint, and you need more of them. Consequently, you are introducing more potential points of failure. They are also a newer product. The full-size LED lights are brighter, just as beautiful from a color perspective, you need fewer, etc. Regardless, with a pool of your sophistication, make sure you get the equipment required to allow you to take full advantage of the lights. By that I mean beyond selecting colors and shows, but control over dimming, motion shows and custom shows. With Hayward that means in addition to the automation system, one needs to add a ColorLogic Network Module. It's only a few hundred but not something to miss on your pool. All that said on lights, with the nicheless, since you'd have more, would look even better with the motion effect working (I.e. like running Christmas lights).
Best of luck with your build.
Be sure to stock up on plenty of POP (pool owner patience) for the process.
