Equipment Grounding Conductor Sizing Problem

I tried to put the equipment grounding conductor size in two of the calculators and that has opened a whole bottle of worms. The problem is the Code requires that the grounding conductor be resized in proportion to the resizing of the ungrounded conductors. This is not such a great problem for voltage drop and I added that to the 310.16 read calculator. The problem is for derating of conductors. This requires that a baseline be established for determining the original size for the equipment grounding conductors. The only baseline I can find is to use 60 degree ampacity for a load of 100 amperes or less and 75 degree ampacity for over 100 amperes 110.14. So each problem has to first determine what the OCPD would be for these temperatures and ampacities then find the correct initial size for the equipment grounding conductor. Then a proportionate determination has to be made for any increase in size of the ungrounded conductor because of derating and voltage drop. The total sum of programming for this just about doubles the program size when adding equipment grounding conductors. Furthermore, for No. 12 and 10 AWG sizes the calculations make the equipment grounding conductor size the same as the ungrounded conductor size. This becomes almost amusing. For instance for a total derating factor of 0.14 there would be a 4/0 equipment grounding conductor for 4/0 ungrounded conductors on a 30 ampere circuit breaker. This just does not seem right. Anyway, I am working on this additional programming for the calculators. Motor circuits are even more interesting.