I noticed there is a SoftTube Mix Bundle that fits into the ProChannel.
 
Is it possible to use other plugins in the ProChannel?
 
Is anyone else making ProChannel Modules?
 
 

Any plug-in can be loaded into the ProChannel. To date, only Cakewalk, Overloud and Softube have made ProChannel modules.

Maybe it can do this, but what would be great is to have placeholder modules in the ProChannel for non PC modules.  
 
When you switch focus to the placeholder, it automatically opens the GUI for the (non PC) plugin you have in the chain.  When you switch focus to another plugin, the plugin gui is automatically closed.

 When a regular plug-in is dropped in the ProChannel, it gets wrapped in an FX Chain. FX Chains can contain multiple plug-ins. Plug-in UIs do not automatically pop up from within FX Chains. FX Chains have their own programmable controls and interface which can be used to control the plug-ins in the FX Chain.