Planning for the best
 

Does anyone have a pretty good idea of how to prepare for installing the add-on? In other words, should I just install it on top of my current install (mods and all included) or should I be prepared to scrub the decks and re-install up to 1.4 prior to introducing U-boat missions?

Is this too early to ask as everyone else is thinking the same thing too? :-?

Just like with any other patch, remove the mods to get it to original version and then install the add-on. After that, wait for the mods to get compatible with the add-on. Some need changes, some don't.