Jerec runs the Gauntlet

Actually, I think you're right.

That said, given that this is Palpatine we're talking about, and the fact that the other dark Jedi are so far below Jerec, he'd have to still be pretty damn powerful to pose any real threat. Plus the numerous other facts regarding his force knowledge and powers, I'd wager he can still progress past Thanaton and Ventress at least.

Sidious cut off Jerec's access to to the Dark Side Compendium when he considered him a threat. Sidious ordered Ventress executed when he considered her a threat.

Ventress > Jerec.

Doesn't seem like sound logic there Zolt, given that Cronal is more powerful than both Jerec and Ventress, yet Sidious merely just transferred his positions.

I don't understand Sidious's logic. If he honestly thought Jerec could rival him (.ie surpass Vader), why didn't he just take him as his apprentice?

He probably thought that Jerec wasn't powerful enough to become his individual apprentice/successor, but was strong enough to challenge him with some favorable aid or circumstances - like the bad middle ground where he's strong enough to be a threat but not strong enough to be a serious equal.

Most likely, Jerec at best could rival Vader who was in no position to overthrow Palpatine anyway, so trading Vader for Jerec wouldn't really give him anyone he already doesn't have...expect one who has lesser lightsaber skill.

The only guy in the Empire, who actually was even compared to Palpatine was Cronal and even then that's only in cunning and intellect. Abit though his knowledge in The Force did surpass Vader and he was quite powerful anyway.