This wont work versus protoss, I mean first thing I would expect when I arrived at your base at around 11 supply, is for you to have lifted off and gone to the gold expansion. If I didn't find you there, I'd then assume you'd gone island and were going banshees. Two gates and a robo will destroy this with no trouble at all. And it will be nigh on impossible for you to expand from that position.
Hmm, kinda. I guess it depends how early I get scouted, or even if they bother scouting me as some people who proxy just get themselves tucked away and don't move (talking Bronze/Silver play here)/ In that case they'd get some units, come to my base and I'm not there, then go looking for me. In that time I could be well on the way to a starport or even started my tech lab for it. Some people may just immediately assume I've gone to the island, some would check gold, some would check my natural expansion, others may just check the whole map before thinking about the island. some may just outright quit the game as Rave found
Also, on the Banshee thing, that's another part of the strat, some people would assume Banshees, but I could easily Medivac drop marines / marauders due to how close the island expansion is to the main base, would take maybe 5 seconds to load in, fly, unload. Plus, instead of killing that 6th SCV, I could send it into a position to proxy something.
Baring in mind though this is for Scrap Station, wouldn't do this on the majority of the others, and I'd rather just go Reapers, MM or just pumping out early maraders before 3:00. Still working on it, might just ditch it, might not... depends how much time this all takes me / what my eco is like / how bad the expanding part will be etc.