Some considerations for this article:
I think your main premise of Island having two different uses in different contexts is a fine one to begin examining the card with, but saying they excel on different kinds of boards is a little too general.
I think calling a board "strong" or "weak" is a little to vague to be useful so I'd just cut out talk of it entirely and focus on what the Island is actually doing for your deck. For instance, money decks certainly want Island's thinning, the difference is they only care about thinning the Estates (or other green cards later), so picking up an Island for that deck has a more specific purpose and you get fewer of them because of it.
"It basically works like other trashers, so you'll just have to rely on intuition. Opening Island is only advisable on really weak boards."
I understand what you mean by this, but Island does NOT work like trashers, and the reasons why are illuminating for why you almost never open with it:
- It's a terminal stop card you need to line up with what you want to thin
- It only works once
It's a tad misleading to say that Island thins your deck by one card. It's not wrong in the long-run, but there's a huge difference between that and, say Bonfire or Cemetery, or even Trade Route which is similar in terms of thinning capabilities, but a more common opener because it works more than once.
I suppose the main point there is that Island's thinning is very weak in terms of getting control of your deck, so if that's the reason you're getting the Island, evaluate your other options and whether or not you need the effect at all.
As far as synergies go, I think you make a few points that either aren't actually good or don't have much to do with Island in particular.
For Workshop variants, I think you can just make this about Ironworks. The other ones are as true for every card under $5 are they are for Island. You make this just about Ironworks and I'm down with it.
Hoard- I'm down with it but I don't think you need to mention buying Duchies or Estates. When you have a Hoard out you usually just buy whatever green card you can (in decks where you wanted a Hoard in the first place anyway) and Island is a cheap one. It possibly disappearing from your deck later is just a bonus.
Copper Trashing- I'm not down with it. I don't think this section is great advice, or specific to island.
Menagerie- I'm not down with it. This is not a particularly strong synergy with Island, the decks you're talking about probably shouldn't have grabbed a Menagerie in the first place.
WW/Apothecary- I'm not down with it. This stuff is true of Island, yes, but it doesn't push you to buy either one of these cards.
Hovel- I'm down with it as long as you mention that this requires thinning the two shelters over the course of a shuffle to be better than just adding a Silver and hitting $5. This is true often enough to be worth a mention but I think you need to say it.
Procession- I'm not down with it. Mostly because it's just pretty weak.
Finally, similar to what I mentioned you should address with Hoard, I think one of the more common use cases for Island is when 2 points is as good as 3 points (you can't or don't want to buy a Province for some reason but you still need to increase your score) and it has the strict advantage over Duchy of maybe being able to disappear one day.