As Ram said, you can customize the Call Entry.
Sometimes, I've seen folks move the entire prompting of whether or not to engage CCB back to microapps instead of in the CallbackEntry application to make the decision point a little more clear.
Also, to your concern about not Queueing all calls in CCB being an issue - calls have to be queued in ICM before engaging CCB. CCB needs the metrics from the queue in order to even offer CCB. This means that all CCB is really doing is taking over control of the PSTN leg of the call so that the customer can drop. It's then also initiating a count-down to re-engage that caller when the math works down to zero, this is the DEQUEUE part of the whole process. Those "Queue" apps are just providing media and prompting to the caller, they are not controlling the actual ICM Queue in any way.
While all of that is happening on the CVP side, ICM still thinks that there is a caller on the line in the ICM Queue because the signaling and messaging has all been maintained by CCB, so whether the call is CCB or not doesn't matter to the queue itself.
Hope that helps clarify what some of those pieces are.