As far as I know, when it's "Free" it can rotate around. When fixed, it dosen't. So, this can be used to line up your ship with an asteroids CoM. And it could be used to say... oh my god.
Two things: One. I like the change in 0.23 of not being able to repeat experiments. This actually gives meaning to return missions and actually makes you need to do something. Two. About robotic arms, TECHNICALLY, you CAN make them in ARM. The CLAW has a lock and free mode!
To be honest, science isn't grindy if you know how to actually get to other planets. Eve, Duna, Kerbin, and all their moons will get you the full tech tree basically.
Yo dawg it dosen't work. So I tried fixing it: Really, I did! okay im bored now Oh come on. Really? You've really done it now. well, turns out yours works now. No idea why.
Yea I don't think KSP will allow 4km without a mod Also, it is canon, so there must be some sort of docking port- unless it's the stati- *Brilliant CLAW idea*