That depends on the sensor / actuator, are you using
"bare" (transducer element, motor winding) or are
you going to insist your user goes with a "packaged"
device with a standardized interface? Both are viable
and the decision comes down to sort of a "make/buy"
value decision on the user's behalf, by you.
If you don't have a clear decision then you have to
figure that the general answer is "yes" (need some
interface layer) at least as a contingency. Though by
some smarts and some acceptance of poorer analog
resolution (e.g. throwing away all range over a volt,
if you have a 0-1V sensor) you can handle more of
the "unconditioned" inputs/outputs, or get by with
lower cost interfaces than a perfectly-tailored
whiz-bang (like producing stepper motor wvfms on
chip and only needing high voltage driver ICs, vs
sending CW/CCW commands via a stepper motor
driver IC of perhaps higher cost). The more general
you want to be, though, the less you want to go build
in a ton of 90%-unused feature options (which will
need something to tell which ones to use, on and on).