This already was suggested some weeks ago and got some positive feedback, so here I come with a complete proposal.
TL;DR: remove non-mutual corporation-wide wardecs and enable wardecs on individual structures for a reduced fee. Attackers will get suspect flag while they shoot at the structure so they can be shot by anyone willing to defend the structure. Anyone attacking the attackers will get fleet aggro so attackers can shoot it back. Structures under attack will be advertised gamewide to allow roaming fleets come to defend or fight the attackers. This will allow emergent PvP and will let tutoring corporations split between go-mutual and no-mutual sections to allow easy PvP progression to all noobs. The loss of blanket wardecs and opportunistic kills of unwary war targets is deemed acceptable as the new proposal enables more PvP and non-mutual blanket wardecs rarely are honored by defenders, who just drop corp or stop playing.
Now for the extended version:
The foundation is to KISS with wardecs: wardecs exist, allegedly, to let the destruction of structures which can’t be suicide ganked. So let them be literally about destroying one structure.
Thus corporation wide wardecs could be made mutual only and add a new type of wardec aimed at individual stuctures. The “structure wardec” would be cheaper than a full wardec (say, cost of wardec / average structures in corp) and non-consensual. Attackers in the wardeccing fleet would be free from CONCORD retaliation but they would get a suspect flag during attacks. This would enable anyone to attack them. To defend themselves, attackers would get fleet aggro and thus the wardeccers could shoot back freely at anyone interfering with them.
Next element, the attacks on structures would be advertised in all game. This way, people could assemble roaming fleets and rush to defend structures -or just kill the attackers for a goodfite. Conversely, wardeccers could use the mechanic to bait roaming “firefighter” fleets into fleet aggro and get goodfites too.
The benefits would be that tutoring coporations could keep a non-wardec corporation that would never go mutual, and a PvP corporation where new players could operate under wardec. Also, non-wardecced corporations would let new players form roaming “firefighter” fleets to try PvP vs attackers, as a gateway to fleet PvP.
The losers of the proposal would be corporations who wardec to get random kills of unwary war targets. But I think (CCP should numbercrunch it with their data) that in general my proposal would generate a lot more PvP. The casual nature of “get in, shoot suspect” to defend the structures would let even Joe Nobody get some kind of defense for his structure, and keeping tutoring corporations free of wardecs so they can decide how and when noobs try PvP would be benefical to the game. Also, targetting single structures instead of the whole corporation would make easier to remove some of the clutter (FAI, think of structures owned by Alliances).
Last, non-mutual wardecs are a mostly broken mechanic and deserve to die. They massively end with a) corp drops b) people stop playing and c) griefing noobs out of game with recurring wardecs that punish them for joining a corporation.
Since structures must die, KISS: wardec structures. Let anyone join the defense at a whim and let attackers get easy kills (or don’t) and/or become easy kills (or don’t). The optimal solution to a wardec should be join a fleet and go facemelt somebody -not stop playing or else you’re the one who is gonna be facemelt.