Is it possible to mod conditions of a challenge?

[Blasted_Taco]

The only challenge i am interesting in modifying just a bit is the You have One Day.

 

So after 24 hours, you get a horde to spawn and go directly into your base while the rest of the map is filled with zombies, however after that day passes, you will get another horde each day until you die.

 

So i am wondering, if is possible to either disable the hordes appearing each morning or having the hordes appear after 168 hours (7 days) instead of 24 hours, i havent seen anyone try to tweak challenges in PZ so that is why i am asking if you can tweak them at all.