Would/could buy margin on additional failures:
1) Upstream NOx sensor
2) Downstream NOx sensor
3) DEF Pump (module)
4) DEF quality sensor (module?)
5) DEF heater (module)
6) EGT 4
7) EGT 5
8) DEF level sensor (module)
Any more?
As a DIYer, the ability to continue my trip, get home, get camper parked, and then source a reasonably priced replacement part is a huge advantage over being far from home and being at the mercy of whatever diesel performance shop that has their own bills to pay.
FWIW, I carry a spare DPF injector in the truck, but NOx sensors and module are kinda pricey.