My apologies if this thread is too old to revive, but I wanted to make some comments.
All games require an artificial conflict of some sort. Artificial in the sense that the players are not really hurt in any way by the conflict. As well, conflict does not imply traditional combat. It just happens that, as was stated, combat is the easiest form of conflict to implement in a digital game.
When thinking of peaceful games, you have a couple options:
1) Completely peaceful, as in no conflict what-so-ever
2) Non-violent, in the sense that conflict exists but there is no combat
3) Pacifist; there is conflict and combat in particular, but the player cannot partake in the combat
I'm not particularly sure how you would go about creating the first one, nor do I think it would create a very good game. A game without conflict would be closer to free play, where a player would just do whatever with the environment without any restriction or game-provided goals. The free play ideas work well in simulations, though there tends to be conflict of some sort (or a way in which you can lose the game).
The second one I think is what you should be aiming for. Conflict can be viewed as "some problem exists and it must be solved". Finding and performing the solution becomes the goal of the game, and you can chain these together. In order to solve the larger problem you must first solve smaller problems, which could create new problems when you go to implement them. Here, I would actually look at puzzle games and other simulations. Harvest Moon could be a good source of inspiration (It's a farm sim in case someone doesn't know what it is) and many of the ideas from that game could be expanded on. I liked how Rune Factory took the harvest moon engine and added combat, particularly with how combat and farming were linked and supported each other. (The crafting ideas they added felt tacked on and unfulfilling though.) Several of the building and environment-altering ideas from Dwarf Fortress could also be relevant. I would also look at the Eggerland series (Adventures of Lolo for the North American audience) as that shows how you could incorporate enemies but provide a way to get past them without really implementing combat.
The third situation would be tricky to implement in an enjoyable manner, as you have to give players something non-violent to do but also throw in combat and a way for them to escape it. Some players may find this restriction rather arbitrary, but it does work in a game where you can fight but are encouraged not to.
The groups you outlined Hajo are excellent places to start with. Focus on the scope of your game, and that will give you a good idea of the activities to incorporate.
