Replace it? No way, it's the game's best feature. GvG is the ONLY reason I still play this game.
REPAIR it? Yes.
The most important thing to repair - REMOVE THE CHEATERS. Not warning, not one week ban, not mild useless sanctions. Any use of bots - OUT FOR GOOD.
The main reason for which most users I know are no longer playing GvG is because it is not possible to compete with bots.
You probably have no idea how far this cheating thing goes.
Here's an example: there's this big guild, which currently has maybe 6-8 users still active in GvG. During the years, these users have "collected" accounts from people leaving the game, and now these 6-8 users are controlling some 20-30 accounts. With these support accounts they created support guilds - currently they have 6 or 7 of those. With these they can open an entire map in one day, they advance by moving each other's HQs much faster than they should, and so on. Those of you who know GvG are aware of the benefits of this cheat.
They use bots from these support accounts also, because they don't care too much if one of those is banned (let's say) for a week. They have reserves.
All this done by 6-8 active users, controlling 20-30 accounts.
There's no way for a guild that wants to play fair to compete with that.
Edit: the admins are completely useless; I've made maybe hundreds of tickets, with the exact time, map, sector where a bot was used, sometimes I've even given them the user, but besides their standard BS answer they are doing nothing. Those users are still not locked.
This game has the same problem as the real world: is far too soft on crime.