You should be able to specifically request a companion in Adventure Mode to use a weapon in their inventory other than the one they'd otherwise prefer. For example getting a swordsdwarf with a steel longsword to use a silver dagger to kill a werewolf, or back you up with archery as you fight creatures in the water instead of trying to path in. When companions have training weapons in hand their combat approach should be training, allowing you to hit them with training weapons and both of you to begin skill training. These could require various levels of trust, as convincing someone to attack an elephant with a carps corpse when they have a warhammer shouldn't be something everyone can do.
Additionally, there needs to be a 'C' combat setting option for the level of combat you want to engage in when move-attacking a creature. You should be able to set non-lethal and your adventurer will try to stick to punching limbs or bashing extremities. Setting it to training should make all attacks the light touches from Arena Mode, but should still be seen as escalating after the first few hits if the creature you're attacking isn't a companion. Wild animals would have no reason to respond to your pokes with gentle taps, and random civilians should be annoyed by getting slapped in the side by a sword, even if it's soft.