I really thought this was going to happen at the last big merge event, but here goes my idea:
Pick a length of time that is reasonable, say, 1 year.
Any account v-moded longer than that time, and, AFTER taking a snapshot of the total account statistics for the account and SAVED in some file database for GF, would be un v-moded, to allow ANYONE to attack and farm. FLEET and DEFENSES could also be removed.
IF at any time the player decides to come back, all Defense, Fleet, would be restored, putting the player nearly right back where they were when they went v-mode.
The benefits to the players actually playing would be tremendous, and give more opportunity for growth for ANYONE wishing to farm.
It maintains GF obligation to the v-moded player.
There is no significant downside for the long v-moded player, unless you count how much further ahead the active players would be. But if that was the concern, they would not have v-moded that long in the first place.
This could all be scripted and once set up, take almost no time to maintain.