Believe me--I understand that Force has a bad reputation and supposedly will not perform up to the standards of Mercury or OMC. I am a Chrysler and Force fan but am also a pragmatist. If the engine is trashed and needs replacing anyway, that is one thing. If it is running well, that is a whole other story.
Unless the Force is simply beyond repair it is not worth the 5K to "Upgrade" for the following reason: You state that "they" said the controls will swap with the Merc.This leads me to believe that the Force is a late 90s engine. When Brunswick/Mercury got their hands on them, internals were changed, ignition was changed to the superior Mercury ignition system, and the lower unit was changed to the Mercury design. The net result was a much better horsepower output. Thus, if the engine is a late 90s and if it is running well, then you will not gain much performance by swapping brands.
Even if it is a lower performance earlier Force engine, if it is running well, It is gunna take a whole lot of convincing to get me to swap for an extra 5K. That's a lot of gas!
At least, that's my story and I'm sticking to it!