Do be careful that only combo decks are going to fall for that trick. Aggro and control decks probably have the removal.
Note that mutavault keeps the ability after reverting to a land. While it's certainly possible they are running removal for lands, it's likely to be much less if they have any.
Get to Legacy and you can reduce the removal numbers down to Bolt and Swords to Plowshares, and then you can up the combo deck density in the meta. Unfortunately, Wasteland is format-warping good and common in Legacy, and decks that cheat in Emrakul, the Aeons Torn are significantly more common in Legacy, and Emrakul's Annihilator 6 will eventually get your Mutavault.
Removal that hits 2/2 manlands while they are creatures is sadly pretty common in Modern. There's Lightning Bolt, Fatal Push, Path to Exile, Lava Dart (both halves combined), Unholy Heat, Kolaghan's Command, Solitude, Dismember, Walking Ballista, Asmoranomardicadaistinaculdacar (more than half the time, she has enough Food)...not to mention generalized removal and bounce like Cryptic Command (yes, control opponents will be that desperate), Assassin's Trophy, and Vindicate.
Get to Legacy and you can reduce the removal numbers down to Bolt and Swords to Plowshares, and then you can up the combo deck density in the meta. Unfortunately, Wasteland is format-warping good and common in Legacy, and decks that cheat in Emrakul, the Aeons Torn are significantly more common in Legacy, and Emrakul's Annihilator 6 will eventually get your Mutavault.
Do be careful that only combo decks are going to fall for that trick. Aggro and control decks probably have the removal.