Suggestions:

• That's really cheap for a permanent Blazing Archon, even if it does take an extra card to get around this guy's drawback. The attack prevention ability should have its own line, and should probably refer to "as long as you control ~" instead.
• "Shroud" doesn't need a sentence declaring its presence. It should be a single word line that comes after the loyalty replacement effect.
• How harsh do you want to be with the "lose the game" penalty? Triggered abilities are easier to circumvent than replacement effects, and I could see it as either.

I like how this follows in the tradition of black card that are basically alternate loss conditions that grant you extra power.

You're missing what this card's really doing: it's a Form of the Squirrel. You can't be attacked, but Cypress can be, and when it dies, so do you. Shroud's problematic, since burn spells almost never actually target the Planeswalker: they target the player and the damage is redirected. I'm sure you're using that as a feature, but most players will play it wrong.

I didn't miss that. What I meant is that if you manage to get around losing when he's gone, you still can't be attacked. I though it was a good idea to avoid that.

Oh, good point. You could always Stifle the LTB trigger, I didn't think of that.

The only way this would work is unfortunately wordy.

"You get an emblem with "You have Shroud" and "You lose the game if you do not control a permanent named ~"." and I keep "Cypress has Shroud." on the card.

Cypress himself still has shroud to prevent Dreadbore and the like from insta-killing it. (Still dies to To the Slaughter though.) Let me fix it.