While it is true that you would need a region owner's permission to use their region for an event, You can't OOCly stop players from entering a town (
Link here) and unless the region is set to peaceful, you can't stop them from attacking people in said town (
Link here). Furthermore, a formal declaration of war should be considered more than enough roleplay validation for attacks to be lethal on both sides, though this might be a bit more clear had the server posted a set of war rules. As discussed also in the new consent rules thread, theft and property damage are also good to go so long as the region isn't peaceful (and so long as the owner of the item or building is contacted beforehand, which a formal declaration of war basically would be such a statement).
Basically, the only real difference is at least giving an event for each attack would let the victims know when the attack is coming and allow for them to pull alts.
The difference between consent-relevant conflict and war is mostly a matter of scale and intent. Revised war rules are still under work, but to clarify a bit of the distinction in the meantime:
The recent consent update applies best to a smaller scale, where conflicts are interpersonal and generally only entail direct consequence to the characters involved. Acts of war generally entail some form of consequence or influence on a region or political entity as well, and while I personally believe that they shouldn't be treated all that differently, player-versus-player consent wasn't designed to handle large-scale conflict as well. It's a component of any larger conflict, but just doesn't account for all the considerations.
A general rule of thumb is that anything intended to affect the region/political entity/organization/what-have-you rather than any individual in the region is probably veering into an act of war, which requires coordination/consent. I'm not going to say that you shouldn't be able to burn Timmy the Turnip Merchant's storefront to shake him down, but wantonly destroying property with the intention of razing the city is not the same thing.
tl;dr Regions require more consent than people.
As to why coordination itself is important:
In order for conquering a place to be a meaningful accomplishment, the defending party needs to be adequately able to represent themselves. Fundamentally, any sort of war involves at least two sides responsible for contributing to the story, and it doesn't make sense from either a fairness or narrative perspective to plan an event for the other side's place without letting them know.
I know metagaming is a concern with any pre-coordinated surprise attack; my ideal state for conflict is that folk will be fair and reasonable about realistically distributing themselves and responding to an attack, but I know that's not always the case. My immediate answer for your summary is that using alts in a war is frowned upon and will probably lead to a banhammer if the other side brings it up. The not-yet-an-answer-but-may-be-later is that a GM-coordinated war may only need the 'when' divulged, not necessarily the 'where.' Both sides would need fair chance to scout/suss out what their enemy is up to beforehand by observing troop movements and whatnot, but removing the element of explicit forewarning and basing it off information that they can glean IC would tidy up concerns of metagaming.
That said, it'd mostly be a way to make things interesting rather than a direct precaution against metagaming. I want y'all to be good to each other, and it's probably a bad sign if you feel you need to lie or withhold information in order to be treated fairly in RP. We'll try to make it so that the rules promote fairness, but still be excellent to each other.
EDIT: Adding a disclaimer that OOC damage to a build always requires the agreement of the owner/builder. No actually burning Timmy the Turnip Merchant's storefront unless it's his build and he's cool with it.
Also, sorry for hijacking the thread. /rerail
