To answer a specific question the OP has - as far as 32-bit plugs running in Bitbridge are concerned, there is little or no cost in terms of workflow. (I can't comment about JBridge as I have never used it).
With Bitbridge there is no additional setup involved as 32-bit plugins are wrapped automatically by 64-bit SONAR.
You open the plugin GUI in the normal way by double-clicking the icon in the synth rack. The only differences I believe are a) a wrapped plugin opens in its own window and by default cannot be docked and b) if you need access to the ACT controls you must open the GUI by Shift+double-clicking the icon. This opens a dockable control panel, from which you can toggle the plugin GUI.
Neither of these has ever bothered me, although I only ever use one 32-bit plugin regularly.
My take on this is that 64-bit SONAR does indeed have advantages in terms of performance and stability, with no penalty in usability.
YMMV.
I hope this helps.