happyhermit
Adventurer
Allowing rangers to be good at what they are meant to be is just a side effect. My primary reasoning is that Expertise fits the ranger perfectly, since they are the only "expert" class that doesn't have it. All of the other classes are much more general in their total concept. The only other additional class I might give expertise is Wizard, and then not until a much higher level than normal. I would say that around level 11-13 they could be considered Experts of their craft.
Of course, my ideas tend to throw balance to the wind, in the interest of what I read as a hole that needs to be filled. For example, I am also considering giving fighters a single Weapon expertise, allowing them to add twice their proficiency to a single weapon type. Because "Fighting man" should be expert at fighting.
Sorry if I came off negative, was mostly just thinking out loud. After seeing 5e with and without expertise I think I am leaning towards wanting it and other pure numerical boosts to skills to be a very small part of the game if there at all. I won't get into why I have mixed feelings about it's effects because it's OT, suffice it to say it doesn't seem to add to any of the reasons we are playing 5e.
From a balance perspective I think you probably have a reasonable proposition though, sorry if it seems like I was dumping on your idea.