That being said, a 1 hour timer is more than enough to prevent crossrealming of any kind of importance.
As it stands, there's enough cross realm transfer of information happening in real time through services like Twitch, the community discord, and other channels.
Realm pride should be second fiddle compared to health and happiness of the server. Logging in to level something Albion while you kill some time waiting for your friends from Midgar to log in should be an option.
Doesn't allow to balance realm mid-evening or fill more groups with people stuck on their timer.
Easy fixes :
To balance the number of groups already out : Allow people that have been on /gvg list for 30 minutes to instantly switch realm via a custom command by the group leader (/gvg switch group <realm>.
To allow for groups to fill : Create new command /gvg switch invite <account name>, that allows a group leader to send an invite to a player logged on another realm. On acceptation by the player, he is logged off and his timer resets on the realm on which he was invited.
While a shorter realm timer would make the opposite possible as well, people switching over to the less populated realm, the majority of people will not, instead they are more likely to switch to the dominating realm of the evening.
On what data are you basing your argument? Most people don't like to do PVE vs keeps guards, I'd say the complete opposite would happen, especially with the bonus xp/rp for underpopulated realm.