Short 'update':

I bought Deus Ex and played it a few hours. It is an interesting aproach, but not that sort of freedom of gameplay that I thought of.

In HL when looking at a close person you can push the use button, and the npc will follow you, when pushing it again, the npc will stay where it is.
That interaction is simple and fast. I'd like to expand this sort of interaction to get more freedom within the 'social' communikation.

New approach:

What if the npc reacts like a Tamagotchi, and the player can offer him food and goods, not only for health, but for mental strength too? Non-material offers like information, like affirmation, like recognition, comparable to stroking(or playing with) a Tamagotchi.

What if the player's character is a Tamagotchi too, which has to get its supply of mental food from the npcs (instead from the player)? Then the player's character can ask for food, for things, for information and for mental support.

This way the player can do both with his character: offer and ask for, with maybe only two different buttons. Deciding wether he gives material support from an inventar or mental support, while he does not choose within a dialoglist, but pushs the 'offer'-button, and hears what the author thought what the character should say in such case!