I wouldn't call making a Sburb-game impossible. TGP exists, of course, and I remember an impressive Minecraft "infinite crafting" mod was released recently that worked quite similar to alchemizing. It's possible, though it would take a lot of effort, and the Homestuck team(s) have enough on their plate already - for the next decade, at least.

From my experience, Sburb is the kind of game that's fun to read about, but painful to actually sit down and play.

Not only is it very easy to screw up your entire game, it's confusing and at times actively hostile to first-time players. The pre-entry barrage of information (on a timer!!) is especially egregious. Even if you've read the comic front to back, you'll probably fail this part at least 5 times before you get it right. I get why it's there lore-wise, but from a game design perspective, it sucks.

As apocryphal as it is, any super-serious "Sburb game" will have to make some major design changes. Personally, I'd start with moving sprite-prototyping to early game (after entry), because this gives a real reason as to why a player should prototype their sprite outside of "because you have to" - the sprite gets made so it can help you in this new world you've landed in!

I do like TGP's stab at it, though. But if I were in charge of making a Homestuck game I wouldn't bother with it...would probably make that "Alternia Online" idea instead.