A servo consists of a motor, an encoder, and some controlling logic. There's nothing magic about that.
If you can find a ready-made servo that includes all components and works for you, then that's probably simpler than using separate components.
In bigger industrial control situations, you typically buy a motor to suit the load, an encoder to suit the precision requirements, and a servocontroller that can read the encoder and drive the motor and receive commands from wherever commands come from.
If you're talking about exoskeletons that need to carry both people and load, you're talking about tens of thousands of kilo-centimeters of torque, and it's unlikely you'll find ready-made servos that fit your overall usage profile. In fact, it's somewhat unlikely you'll find many motors and power systems that will fit the general weight requirements at all... There are some Darpa projects around for building working exoskeletons to support things like loading missiles onto airplanes and whatnot. You can find videos on YouTube.
Note that anything that goes onto a human being pretty much *has* to be at the level of sophistication that those research prototypes use. It's not likely something you can build out of cheap, ready-made parts. Yet :-)