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