Spoiler:
What it does however is give a very convenient way for people who queue for SCs to, let's say it out, leech: leech zone locks (that they did nothing for, as they are queuing in the keep) since most warcamps aren't part of the lakes, but all keeps are, and leech the usually easier defensive keep sieges. At the moment, if a premade scenario party wants to take part of a keep defense and the advantages it has (NPCs dealing damage, better terrain, likely AAO), they have to ride to the keep, then go through the hostile siege force and into the keep itself. As far as RvR action goes, this has its advantage since they will probably fight the enemy's backline. And it most certainly has the effort-reward and that risk-reward thing you brought up, specifically that if you want Open RvR rewards, you will have to show some commitment and take the risk of going through a much larger force (or be part of the main force in the lake that was there before the siege and if successful, likely will be afterwards too), not just expect the RvR literally to come to your door while you do something else.
These people are also kind of a liability in the lakes due to their unreliability. People crash and logoff all the time, but you can generally expect people you see in the lake to actually want to be there and stay or come back, not just hang around because it's convenient for them at the moment and then disappear into a scenario when you need their support and you suddenly find yourself facing a much stronger force than you expected.
Under the current conditions this would probably lead to an increase in people joining scenarios while in the lake warbands, unknowingly or intentionally. Until the devs manage to find the cause of that bug and fix it, this will remain a concern.
On the other hand it will limit access to economically vital NPCs (how much they are so can be seen from the recent adjustment of the kill quests and the playerbase reactions). MMOs show quite clearly that people don't really like grouping up. Even in RoR you can see that people prefer the most casual way of grouping possible, such as open warbands for the lakes or solo queue options for scenarios. Whenever there is something they can reasonably do solo, a lot of people will opt for that: you can rarely see parties outside the lakes, while solo players you'll run into very often. This isn't even necessarily poor behavior as much as just part of life: players don't all have the time and, with the rest of their real life activities, energy to handle the time/effort organised groups require (not to mention organised groups always have an advantage that this playstyle forfeits, no matter how the game is set up). This is a constant source of arguments on WAR/RoR since it is very group-oriented, but casual players are still a large part (I personally have the impression that they are the majority) of RoR's, and most likely any MMO's, playerbase. WAR live tried to cater to these players with the quick and easy open PQ/lake/scenario party system.
One of the consequences of this suggestion, that you say would improve the Open RvR, goes exactly the opposite direction: you need to be in a group to be able to do something very basic you were able to do solo before and doesn't involve others, which doesn't even have anything to do with the Open RvR itself (at the moment at least); not simply joining the group and catching up with it wherever they are in the lake (as it is now), but being close to them before even going into the lake as you need their support. Being able to turn in a quest that you already completed isn't really a "reward" that you need to work hard for. There is a proverb I think is very appropriate here: you can lead a horse to water, but you can't make it drink. If people want to participate in Open RvR, they will do that without being forced. If you try to force them into it, they will more likely only do exactly as much required or just abandon the whole thing, plus they will lose some interest in the game as they'll feel mistreated and possibly just leave eventually.
It will also encourage people to camp the enemy's warcamp, keep and the road in between rather than bother with the objectives in the lake. That is, constantly, instead of just during sieges when they essentially form a blockade and actually contribute.
Everything considered, I think the join and return from scenarios inside keeps option, and moving warcamp NPCs and mailbox there would both make Open RvR worse. It's better to keep those activities as seperate as possible, and let people decide which of them they want to do at the time.
