Yes, it's a stupid concept because it tries to one-up the Death Star, but I'm not going into that here.

The Sun Crusher is stupid from a logistical, operational, and strategic standpoint.

This thing is ridiculously vulnerable to theft next to the Death Star. The Death Star has a crew of thousands. You cannot hijack the Death Star and run off with it. When Palpatine was concerned that Tarkin might turn the superweapon against him, he installed Vader as a watchdog.

Obviously, he felt confident enough in that arrangement to leave Tarkin in charge. Tarkin cannot press a button and blow up Coruscant on a lark. He needs to give lots of orders that go through lots of people. He needs to pull off a fairly complex coup if he wants to go rogue with the Death Star. Vader will have ample opportunities to stop it.

Unlike the Sun Crusher.

Who will Palpatine possibly trust enough to put behind the controls of the Sun Crusher? One man can, in fact, press a button to blow up Coruscant (on a lark). Palpatine may not even see it coming! It targets the sun! Is he really so confident that one pilot can't be bribed or compromised by ambitious moffs? That no one can hack or reprogram a droid pilot's brain? That the ship can't just get stolen? Is he going to gamble his reign on this? He only gets to be wrong once.

The Sun Crusher's lack of human and technical safeguards is ludicrous. In the real world, the bombers that dropped Fat Man and Little Boy had crews of 10 and had too limited a range to bomb anything besides their intended targets. In the real world, nuclear submarines have crews of 100 and safeguards to prevent commanders from arbitrarily shooting nukes at whoever they want.

The Sun Crusher has none of this. Its sole crew member can destroy whatever solar systems they want, and has a hyperdrive to fly anywhere in the galaxy they want. Dear gods above--why give this thing a hyperdrive?! At least without one you have more control over where it's deployed. Marginally more. Since it's small enough that even an individually piloted ship like the Jade Shadow could make off with it...

Because let's not forget, the Sun Crusher isn't just a one-man ship. It's really tiny. It has nowhere near the psychological impact of the planet-sized Death Star. The Tarkin Doctrine calls for fear of force to keep systems in line. The Death Star works just as well as an instrument of fear as actual force. That's in the Empire's interests, because why blow up an entire planet when you don't have to? The Death Star can terrorize fleets and planets into submission through its presence alone. The Sun Crusher is too small to effectively do this. It has just one use: force.

This is a weapon better-suited to genocidal terrorist groups than a galaxy-wide state.

Destroying a solar system is overkill next to destroying a planet. I do not think the former will terrify dissidents appreciably more than the latter. But if you absolutely must have the biggest space dick, why not rework the torpedoes into projectiles the Death Star can launch? Ideally ones that won't function without a superlaser so that, you know, someone doesn't try to steal them. Hey, would it be possible to steal the Sun Crusher's torpedoes without stealing the ship? Oh my god, it might be. That's probably even easier to pull off. Where do these torpedoes get manufactured? What would it take to produce your ow...

I can't go on.

The Sun Crusher is a moronic weapon. It is inconsistent with Tarkin's philosophy. It is a greater threat than asset to Palpatine's rule. He should execute everyone involved in its design and destroy the schematics.

It's so stupid.

End rant.