Me I would just drill through to Loch Vrotachan which has the added bonus of no or little pumping required, and a lot of water.
Me to. Its seems pretty sensible and that loch collects plenty water naturally
Of course, the claybokie, plastic slope poma and dink-dink already have power & water lines installed. I even have a photo somewhere from circa 2009 of 5 fan guns all running down claybokie, probably only with 1/3 of the nozzels spraying though. Looked good.
I'd be all in for a snowfactory there at the Cairnwell resteraunt, feeding all of those lower runs with conventional snowmaking up the racetrack and up Cairn Aosada.
Sunnyside is tricky, partly due to the low altitude (only 800m at the top) and because I'd rather see an area be developed that has already got 2 new chairs and will have a 3rd soon - kinda like grouping all the tech together for successful early and late season skiing. Theres no point in spreading resources to thin if the end result fails to make a difference.