One of my players wants to be a sorcerer, in spite of my warnings. I generally believe in giving people the rope they want to hang themselves with when the ask for it, so I have it all plotted out well enough in game.

Looking at the rules though, I find them a bit lacking. The official Rogue Trader sorcery rules in Edge of the Abyss are pretty bare bones, but mechanicly compatable. While the sorcery rules in Radical's Handbook (for Dark Heresy of course) are far more interesting, but of course not really mechanicly compatable.

Is there a more robust sorcery system that is more compatable with Rogue Trader in another book?

My two main issues are:

1. I have an astropath who seems to be working well enough and would rather not change how he works.

2. I was dissapointed how the Rogue Trader/Edge of the Abyss system didn't give much if any Corruption for casting spells.

Any input or advice would be welcome.

I think you are on the right track with the Dark Heresy systems, especially at the bits about Radicals and Istvanians. Though Black Crusade might be spared a glance, too.