Instead of having the ProChannel optionally before or after the FX Bin, I believe that the ProChannel would be better inside the FX Bin and represented by a placeholder as though it was itself a plugin. Maybe a different colour would distinguish it from individual fx. Clicking on it would open the ProChannel. There would then be no need for the pre/post option, as plugin fx could be placed both before and after as required.

Some people have complained about the ProChannel and FX Bin being separate in the GUI, making it confusing for new users. This might be a good way to integrate them.

You can accomplish exactly this but in the opposite direction by using the ProChannel's FX Chain module.  You can add as many FX Chain modules as you want so it allows you to intermingle plug-ins with ProChannel modules however you'd like.  You can even drag n' drop a plug-in from the Browser view to the location you want in the ProChannel and SONAR will automatically wrap it with the FX Chain module for you.  
 
I personally would prefer if it worked the other way around like you suggested.  I find the ProChannel takes up way too much screen real estate and prefer the convenience of being able to see and access the normal plug-ins on the Track and Console views without digging into the ProChannel.  

Dave76
You can accomplish exactly this but in the opposite direction by using the ProChannel's FX Chain module.  You can add as many FX Chain modules as you want so it allows you to intermingle plug-ins with ProChannel modules...

 
It would also make sense for the fx in the FX Bin to be displayed at the top and bottom the ProChannel too (maybe as FX Chains or maybe not). This would mean that all the effects being used on a track could be visible and accessible in one place in the correct order, top to bottom.

I like this idea.

IN ADDITION:
The (proposed) ProChannel placeholder in the FX Bin should also have some sort of indicator to show whether or not any of the ProChannel plugins are active. Currently there is no way of knowing which ProChannels are active whether opening them one at a time.

great idea!
Sometimes having the "sidecar" open is a bit confusing during mixing; It certainly looks great but it breaks the symmetry of the channels and to me it looks like there's too much going on.

If there were 2 bins, one for PC and one for Vst FX, the bin wouldn't take up as much track height with everything showing in one bin, you could see both sets and their statuses, and pressing the pre or post in each box (or on the console) could swap both their signal chain and position on the track.
 
 

This post is not related to the post above. I think this would need a single FX bin on the track. Have the VST fly out like the Quad EQ
 
 

Kamikaze
If there were 2 bins, one for PC and one for Vst FX, the bin wouldn't take up as much track height with everything showing in one bin, you could see both sets and their statuses, and pressing the pre or post in each box (or on the console) could swap both their signal chain and position on the track.

 
Having them side by side would defeat the purpose. I want to eliminate the need for pre & post (by having both) and for the ProChannel's position in the sequence of fx to be represented visually.

I like your flyout idea though.