Could you use the "Solatube" system? Then the hole for the skylight would have a minimal effect on your ability to use your roof deck.

Having rood-lights in our kitchen, dining/sitting area, and, with recent summer temperatures, light, glare and heat should be your main considerations - not symmetry. Consider your orientation carefully. Our back garden is NW and the architect placed roof lights to assist with light penetrating into adjoining rooms and obviously for our extension. Light in the area is generally great. However, we did not consider carefully enough glare and heat during summer months when sun is high. There are spots in the room that have necessitated shades during summer months in the dining/sitting area. We do not watch TV in this area but, if you intend to have a TV in your family room, consider the location of the roof lights carefully. Best of luck with your project 😀

Our island is 2780 long, and I believe 920 deep where the bar seating will go, otherwise probably around 600 after the curve in the narrower section. We are doing this curve to give circulation space behind our sofa/snug as it could be a bit tight, you may not have this issue though! We're going to try keep 1000 for the walkway between units and island, I think this would be comfortable, and if we need we can reduce this up to 900 but I don't want to do that. I think of it in terms of not compromising on the practical ise of the kitchen area - as there will be multiple people passing between while cooking, I feel it's nicer to have that space instead. We are having to keep 800 from the island to the end doors/wall though, as we need to shift the island down as much as possible in order to give a decent circulation space between the island and the snug! We would like to have bench seating for the dining area! It's something that will look into after the main stuff is done, I don't think space will be a problem otherwise. We are hoping to fit a little snug in - but will have to see one the kitchen goes in! Depends if we find the right sofa really to fit in there but we'll see :) We marked out dimensions on the floor using masking tape before any works started to get a feel and understand how the dimensions translate to real life. Our extension was existing, done by a previous owner, so we only had the space we had to work with as we didn't want to do more in that regard. We’ve changed the flooring throughout the ground floor, added in a utility (actually made our existing open plan space a bit smaller!), will add in the skylight to bring more light in. And otherwise paint and all that kind of stuff, so nothing majorly structural. Hopefully if you have the ability to make it yours and have some space to play with, then absolutely go for it and I'm sure it will fit! Especially as you have a bit more length, your island can go a little further back and give you enough circulation space to the snug, which is our main restriction. How exciting that you start so soon though, wish you all the very best with it! I will post pictures soon once I get some :)

Artificial window or skylight similar to what Prosky, Coelux, and Pesetech offer, and I'm in Canada :) . Pesetech and Coelux have IP54 and IP65 rated lights, but they are too large for the wall or ceiling. I've asked around locally, but haven't found answers yet. I need an IP65 (or damp rated high enough for a bath alcove) for it to pass inspection.