A few conclusions:
Friendly fire
This is what I want to see:
- Arboreus: PvE without friendly fire
- Syndesia: PvP without friendly fire
- Tartaros: PvP with friendly fire
Imposing friendly fire on Syndesia would remove a significant choice from the game, and "disenfranchise" a significant number of players.
Collisions
While I understand the desire for player-to-player collisions (more realism and immersion), collisions are expensive to develop and model. Consider, if you will, an Albion Online reset day with thousands of players zerging. AO does -not- have player-to-player collisions, but what if it did?
The servers suddenly have a great deal more work to do: tracking collisions between every last player across the world, notifying clients of legal movements, and being notified of proposed movements that must now be verified against other moving objects. That would only make the lag issues in AO worse, and imagine what lag would do in -that- situation!
Furthermore, while I understand the argument to allow collisions on even one world for the sake of choice, in this case, I see it as an all-or-nothing proposition. Why? Because every weapon, every skill, every attribute should be expected to behave differently in collision-based combat versus non-collision-based combat.
The developers would thus have to balance everything against two very different combat systems, and that would be a nightmare.
So, my vote (if it matters to the developers at all), is against player-to-player collisions.
Conclusion
Arboreus is PvE, and Tartaros is no-holds-barred, anything-goes PvP. Syndesia, however, is the balance between the two, the neutral world between good and evil. It should not be surprising if Syndesia winds up with a significant number of PvE-like protections in its PvP.
At that, limited PvP -is- possible via invasion on Arboreus, and demons get periodic free invasions of Syndesia, thus the balance of the world of Fractured is already tipped in favor of PvP.
It doesn't need to be tipped further.