I bet a lot of you missed this. Unless you read through all four (4) pages of posts on the Installation page of the LM Forum, you probably didn't catch it. Just a short post from Adam Breed.
"Future releases will incorporate an installation procedure that is similar to your comment. We will provide detailed information once our new patching/installation procedure is completed.
We definitely do not like to force the 10GB download on everyone more than once!"
Adam Breed
Prepar3D® Senior Software Engineer
So, looks like LM want to make life easier for us in the future.
He is talking about a patch type update install, vs a full uninstall/install.  Since LM changed file structure in this V2.5 release, I guess they had to do a full install. They must have a long range plan here for doing this.

Yes, that is the precise reason why v2.5 must be a full installation. It also means that third-parties will need to adjust their installers to use the 'new paths' and keep their (our) stuff out of the Prepar3D default folders...

 

...although how scenery devs are going to avoid replacing default scenery files remains a mystery.