Instead of forcing a new update on to people they should just add hardcoe Mode +1:
- All three meters raise 3 times as fast
 - Ammo weight doubled
 - Ammo looting from both NPC's and ammo boxes reduced by half 
 - Vendors having 50% as much ammo as they currently have
 - Radiation is doubled or even trippled from everythin. (Casual or norma hardcoe mode give +5 rad from drinking from a radiatied sink, while in HCM+1 you get +15 rad/sec)
 - Healing radiation, crippled limbs or drug withdrawal costs around 500-1000 caps at a doctor.
 - Implants price is trippled
 - Repair costs from repair NPC's costs 50% more
 
And then hardcoe Mode +2 which does all of above but also does this:
You can't fast-travel from where ever you want to now, you have to be in the vicinity of a town/outpost/city to travel to another town/outpost/city.
But you cannot travel from let's say Abandoned Shack to Vault 22.
This would be completely optional, both options. And would really crank up the difficulty.