Wait, so... this triggers from your library? Do you just explain to your opponent that you have this in your library and that's why you've begun a search? I don't think things should trigger from hidden zones.

Yeah; I think that makes this silver bordered.

Maybe have it trigger from sideboard? Or is that even worse?

There's at least one card in Legend of the Five Rings that you reveal before you begin playing, so you can search it up at some point during play. I always found it odd that Magic never made a few cards like that, considering how much design space that game burns up. Maybe they're saving it. The mechanic could be a bit of a bummer, killing the surprise.

Some cards, however, like the Infernal Spawn of Evil are made more fun by giving the opponent the warning. A card that fetches itself when a state is hit (your opponent has no cards in hand, or their graveyard has ten cards in it) could also be fun.

They got close with Panglacial Wurm, but I think there's a rule that prevents things in hidden zones from triggering. See what happened to forecast, which is obviously meant to be an upkeep trigger. (E.g. Skyscribing)

Fair. But "Before the game begins, you may move this card from your library to your Command Zone." would probably work. Or something approaching that at least.

I think the rules could work if a card said, "before the game starts, you may reveal this card. If you do, whenever [trigger] you may [search]." But they've avoided that because it's a lot different to normal triggered effects.

They've also avoided a lot of other "this card takes effect just by being in your deck" which could be implemented by a "before the game starts, put this into your command zone" clause, like commanders, like the bosses in events for the theros release, like avatars, etc. Which makes me think they want to stick to a library model most of the time.

The other problem with taking stuff out of your deck is - why would I not just shove 4x each one in my deck - purely so that I can play a 24 card deck, and ignore them?

Exactly. Maro answered an ask about this relatively recently: it was a mechanic he was hopeful about but turned out to be a spectacularly bad idea, because it removed variance.

See also the Conspiracies like Immediate Action, which are a way to do this. You could have a conspiracy that starts face down and says "When you attack with three or more creatures without first strike or haste, if this is face down, you may turn this face up and create a 2/2 red Superhero creature token tapped and attacking."

But the key thing about conspiracies is that they don't count towards your 40 (or 60) cards in your deck, so you don't get deck thinning along with your consistency.