I found the same problem and removing the hard coded list would be good. Strec might be able to use the <Addto x> function here but it would still be fragile http://strive4power.wikia.com/wiki/Modding_Guide.
Putting an empty customdayend() function and customslavedayend() function into the end of day at the right points would allow modders to add their own custom processing without touching the main end of day script.