Please consider adding this issue (how do you build switchable force fields?) and its resolution for the FAQ...
http://forums.sjgames.com/showthread.php?t=61975
You may want to check and get a more firm ruling, but it looks as if Switchable is
not required for DR (or other passive abilities that are usually Always On) to make it "usually off"
if it is built with a limitation that implies it is usually off, has to be turned on, and will only last for a certain amount of time, and will then shut off whether you want it to or not...this would include Requires Concentration, Costs Fatigue, Trigger, Accessibility, etc.
In short, the reason Switchable, +10% is an enhancement is that it gives you a great deal of control over when something is on or when it is off, at no extra cost. If something can take that ability away, then the power is Transient, and you don't need Switchable, +10% to build it.
Mark