At least Very Hard should be cranked up a few notches. Your damage output and healing rate remains the same, though enemy damage is increased 2x. Enemies don't need to be bullet sponges or a scarcity of ammo, but more things like:
- Enemy AI will fight more strategically by flanking more often, chasing you in formation using point and cover, throwing grenades while reloading
- Enemies showing up in greater numbers, sometimes even shooting flares to call for back up, keeping you on your toes
- More behemoths and gigantic versions of enemies like mole rats, scorpions, stingwings
- Certain enemies like behemoths and deathclaws will always be higher levels than you to avoid one-shot kills
- Human enemies and Super Mutants can heal themselves and comrades by using stimpaks in battle just like you and your companion
This could be a fun alternative for anyone who wants a higher difficulty without playing a revamped Survival, worrying about food and drink.