Lurking a bit. Didn't see a suggestion area on the github so I'm posting here. I'll toss in my thoughts on structures and how I feel they should be approached if you were looking for ideas. Brainstorming is fun. I used to work on a game in Unity3d and I used a similar mechanic in it before it went up in flames. (rip HDD)
Structures will need to keep 3 things in mind:
- Capable Of Retrogen in older worlds.
- Incapable of being griefed or being used to grief.
- Unique in each instance.
Anyway, here's the gist.
-Generate "Pillars" throughout the world. Not super large, magical looking etc. (3000> blocks from the origin. Each must be at least 200+ blocks apart.)
-Each "Pillar" is unique. It represents an Element (fire, earth, etc) and there cannot be more than one of each "Pillar" in the world.
--These pillars can be activated with a spell, key or whatever prerequisite you'd like. Then a portal appears at the "Pillar" for 10-15 seconds.
-Entering the portal will teleport you to a "chamber" where you can fight the elemental guardian of whatever type of "Pillar" you entered.
-After your boss battle, loot drops or whatever and then you have 30 seconds to get the hell out through an exit portal before the "chamber" collapses. (Kills you.)
-After you're back in the outside world, the Pillar disappears and a new one is generated somewhere else in the world.
The key idea is that these "pillars" can be used to create small or even large areas of playable content without directly impacting the worldgen in an obtrusive or repetitive way. At the same time, the aspect of them disappearing and generating in another location is meant to make Ars Magica not only more unique and interesting, but perhaps also contribute to competition on MP server. (Ha, I destroyed the Fire Pillar near your base; Now all that magic stuff inside is mine! I'll be the best sorcerer that no-one ever was)
In regards to what Aridhol was talking about; having "chambers" that can be entered also opens up the possibility of having a full fledged magic town inside. Perhaps more enduring chambers / content areas should be grief proof somehow. I had originally imagined spheres for the chambers that were invisible from the outside, but allowed people inside to see out. Could be something similar to how 3 strongholds are generated in each world for something like a magic town. I'll put the inspiration of that is somewhere in between Harry Potter and Dalaran -- take your pick.
Finally, generating "Pillars" doesn't sound too difficult but you might be wondering how to implement "chambers." Originally I figured another dimension being generated would be the simplest solution although it could be a turn off to some server operators. Maybe generating the chambers underneath bedrock in the same chunk could be a solution. Who knows.
That's my 2 cents.