[color:"orange"]why you can do that but not that[/color]
Well, every 'that' has to be programmed in and graphics created or updated for the result, so there has to be some limit. More would be better, though, as long as it doesn't take so much time to implement that it interferes with other parts of the game.
I am not sure that every interaction need to be programmed but more need to be parameter. For example many interactions can just be the drag and drop general management and from this base it's a table like X+Y=Z or X+Y=X'+Z or X+Y=X'+Y'+Z . Yep the table could require some more columns like to check character conditions. But basically those sort of interaction are all the same just parameters, at least if you don't want to program fancy animation for each interaction/change.
But ok I must admit that interactions like that coud require to create for the result a new object that otherwise the game doesn't need. So in those case it's more programmation/Graphics. Anyway I quoted many interactions that I tried and didn't work (but perhaps I did something wrong or haven't a required skill).
I also admit as you suggest that it's just one part of the game and it should not eat other parts in the budget! But I feel that games gave up on objects interactions so that point could be something different particularely in RPG and that's important. The difficulties is :
- To have a clear interface, not sure DD has it, perhaps Beyond but not obvious.
- Be quick to understand and deeply understood because it's not common in RPG games and that's where the tutorial is almost required.
- To have logic that's where limitations could discourage player bored to try many interactions that doesn't work or with not hint about how make them work.
- To use it in manny puzzles and have hints to help players get through numerous possibilities, that will force the player to learn the depth and possbilities.
Ha well it's funny to dream.