I am thinking on going with a skeg control in my boat that is similar in design to Et's, i.e., the cable is not housed in a metal tube within the control box but is, rather, left bare. I can see there being the possibility of kinking the cable if pushed hard enough but I think that if you have to push that hard, then the skeg is jammed and should not be forced.

I've only built one skeg system...so not an authority at all. eT's control box has plenty of use on the water, I assume, so it should be fine. That said, it's not something I would have on my boat. I don't think much of the typical cable setup at the skeg box either (cable free inside the box, entering from the top side of the box); that's why I used Reg Lake's (innovative/excellent) idea to support the cable with side entry into the box, and a channel in the skeg blade. Cable kinking is something I'd do a lot to avoid.

I am thinking that leaving the cable bare, while initially seems like it is exposing it to the salt water is probably better in that water will not get trapped in the tube and cause corrosion and such.

You'll have salt water at the other end of the cable anyway (at the skeg box). It will take a long time to corrode away, I think.