Interestingly the CN God of Random could just hand out a randomised list of spells - so these two opposites could work, though that could mean that this is just very mutable fluff.
I would not like to do this as a DM for several reasons
- It dis-empowers the players and denies player - agency
- It increases the DM's workload
- It also puts the DM in a difficult position: does the DM choose the appropriate spells for that days encounters; or does he take the blame for choosing the wrong spells even though he knew what was coming and thus stitched up the party ?