Well thats bunch of speculations. Sasuke has PS now, lesser versions of susanoo arent so taxing any more. He could use summon susanoo and enton all together, i dont see why amaterasu would be a problem, not to mention that sasuke already used susanoo and amaterasu vs danzo.
You're the one making weak argument for the sasuke, yet for kakashi its ok?
What is the "weak" part in saying that Kakashi can kamui Sasuke because he can focus his eye on him and according to databook that's all which is needed for Kamui?
How I see it, my argument is based on common sense and databook.
-Does Kamui appear on the target instead of travelling? CHECK
-Does Kamui appear wherever Kakashi focuses his eye on? CHECK
-Can Kakashi focus his eye on Sasuke in Susanoo? CHECK
Your argument, on the other hand, seems to be the argument from ignorance - you ASSUME that Amaterasu can't be used through Susanoo and then you speculate it's the same with Kamui. It's wrong on several levels:
1. You have no proof whatsoever that Amaterasu, in fact, can't be used through Susanoo
2. You have no proof that it would be due to Susanoo's properties and not Amaterasu's (for example if Amaterasu travels)
All in all, I can't help but think your argument weak.