I have kinda mixed feelings about the first part, not sure how Toady would feel if DF was known for having way too many ways dwarves can commit suicide.
The second part, about adventurers being able to target themselves with attacks has come up before and i do think that would really make it easier for the player to for instance spread vampirism by offering mugs of their own blood without having to get into a risky fight. Or amputate infected limbs. It would also be nice on that note to be able to ask companions to let you amputate infected limbs for them without starting a fight and scaring them off/having to kill them. If they trust you enough. Probably a medicine rewrite thing tho.
The last part, retiring/starving to death could use some work, like maybe the option to retire even in the wilderness, and they'll go to the nearest inhabited site or a ruined site if there are no inhabited sites left in the world or making their own empty style bandit camp if its one of those bizarre worlds that never had civs. If you really want them to die, there are dozens of ways to quickly off yourself, like picking a lethal fight with the wildlife while naked and just lying down and letting them eat you. Or setting the grass on fire and standing in it.