Ideas are always welcome. :)
You're probably right about single-use potions and crafting. It would be better to find the recipes in the world, especially since they should be valuable and not a viable choice for salvaging.
As for the fortress, well, I'm just going to provide building blocks and let people have fun however they wish. ;) If everything goes well, in v0.4 there will be a lot of new possibilities with modding too.
I haven't thought about fighting on different z-levels, not sure how well it would work. I'll need to change AI to start thinking in 3 dimensions, but casting spells up or down might be too easy. Technically it could be doable, right now when we walk in the world, 11 region maps are loaded at the same time, including one directly above and below. It would probably have to be expanded to more regions to cover the edges, so would have to be optimized some. Then again, it would be so cool to fly above ground or have flying enemies... I'll add it at the bottom of the list for now, and we'll see if we get there. :)