Throughout CRRCSim lots of non-SI units are used.
I clearly state that I did brake this scheme for the new power system, which
is SI. It has a clean interface to the rest, therefore it is easy to
understand where there is SI. I'll try to convert lots of things to SI if I
can.
Exceptions are for example a batteries capacity (Ah instead of As).

It seems to me that one of the misfeatures of this 'other system' is that you
have several units for one thing, for example ounce (oz) and slug. The
latter seems to be needed to be able to write
  F = m * a
  1 pound-force = 1 slug * 1 ft/s^2
Something like this makes clear how easy and comfortable SI is.  

1 foot             = 0.3048 m
1 slug             = 14.5939041995 kg
1 oz               = 0.02834952312 kg
1 pound, lb        = 16 oz = 0.453592 kg
1 pound-force, lbf = 4.44822 N

force: F = m * a = m * s / t^2
       1 slug * 1 ft / s^2 = 14.5939041995 kg * 0.3048 m / s^2 = 4.448222 N

Velocities:   ft/s
Acceleration: ft/s^2
Forces:       pound-force, lbf
Moments, inertia:
  1 slug ft^2 = 14.5939041995 kg * (0.3048 m)^2
  M = J * alpha
So moments must be in 1 lbf * 1 ft = 1.355818 Nm