Invasion - Kafer war - boring.
Just my opinion of course.
Unless you are going to retcon it we already know all the details and will not be buying it. I bought Bayern instantly, it is in my opinion one of the best products you have put out there, but the Kafer War arc doesn't interest me one bit. Unless you offer something new that is
Research station attacked by unknown aliens.
Aliens return in force and attack worlds on the French Arm
For some reason the French stop being the evil empire and everyone rallies around the French
The Amrericans have the bestest bestest ships, and their marines are the bestest bestest and so the fight is taken to the Kafer
A back door route is discovered into Kafer space and a small recon mission learns really important stuff about the Kafer.
Fast forward a bit - a pentapod bioweapon is used to kill all the Kafer, thus proving the Kafer were right to try and exterminate us first.
The end.
1. The Kafer war should involve the French arm countries only. Yes, you are playing a French character. Until the scale of the threat is realised it is going to be the French vs the Kafer (I wonder how much damage was done to the 2300AD line by having the French replace the Imperium? Ever notice how quickly they moved away from the French being the most powerful multiworld government?)
2. To maintain my interest of an actual war setting you will have to give me the tools to include such in my game - fleet combat rules for ship to ship engagements, large scale battle rules for the pitched battles against the Kafer. Those i would buy.
3. A retcon to the final solution is needed. Pentapod bioengineering offers so many possibilities, but firs the secrets of the pentapod must be discovered (the secret of the pentapod gods was revealed much too early in the metagame, this knowledge should be a secret for a long time).
And now back to the OP, it is pretty easy to use any of the old adventures, even the GDW ones, with the new rules.