The Ultimate Unity Development Workflow - including shared Asset Library, version control and team collaboration

I've been trying to figure out the best method for a proper Unity Development workflow which would include Asset Library (shared between projects), version control and team development per-project basis. I've been reading a lot of posts and questions / answers and I still haven't come to a definitive answer or if this even possible without forking a lot for it.

This following screenshot should explain roughly what I'm after (see bigger version here):

Now, I've got a couple of quesions:

1) Where to store the Asset Library and how to link this to Unity

2) Where to store version control (without asset library)

3) Best way to collaborate per-project basis

On 1) - Until now, I have stored all my assets locally (OS X) and used Symlinks to link the Asset Library (or even Symlinked subfolders only) to each project as needed. This has worked well with Prefabs, Scripts, Models, Tex etc etc. .. Until now: In preparation for 3), I want to store this library in the cloud.

Problem is that Symlinks in the cloud is just a no-go.. What tends to happen is that any symlinks are turned into their own folders, duplicating the Asset Library per project: bloated projects & no unified asset updates.

How can I store this Asset Library in the cloud and expose it to each Unity project and ideally only the folders/directories I need for that project (not needing 3D assets in a purely 2D project).

On 2) - Reading up on this seems to suggest that Github seems to work well in terms of version controlling certain aspects of the project and excluding others (i.e. Asset Library). What about SVN? Could I somehow solve 1) using svn:externals? How would this work with a cloud provider, say like Amazon Cloud Drive or Google Drive?

On 3) - What would be the cleanest, most straightforward way to allow other developers/artist access specific projects, ideally even only certain parts of the Asset Library using this setup? I guess the simple answer is to use Unity Collaborate and I'd be happy to use is as Unity Personal, apart from the storage limitation of 5GB. If I can have the Asset Library stored somewhere else (i.e. Google / Amazon), I assume this would be an ideal solution? What about other solutions, how do people find working with Github on team projects?

So, what I'm after is a cloud-based Asset Library and a Per-project team development workflow which would include version control.. not asking much! ;-)

I already own unlimited Google Drive and Amazon Cloud Drive, I'd rather not pay for another cloud storage (i.e. Unity Collaborate, Plastic SCM, Perforce).

I would really appreciate any input on this, especially if you have something similar already set up.

Many thanks, PJ