If this was a flag that could be purchased, I think that it would need a much higher price than the current $10,000 for flag changes.

 

I can see many problems with this, however I can't think of any of them x(

 

This could be easily exploited, I think it's a bad idea.

 

The problems that could exist are people in arena's and mobspawners, but arena's override normal town flags and you can already mobdisguise and make the mobs not attack you and I can't think of any other issues.

I would really like this seeing as my town is underwater and with this I can mark out plots easier and I wouldnt have to take in account that people can drown.

 

I agree with you. But you can't have these flags with it something like this?
[]MobSpawn with Invincibility
[]PvP with Invincibility
are some that wont be aloud?

 

think of obsidian harvesting.... i don't harvest it cause i hate lava. bad idea i think....