In all honesty, we didn't have this when mobs in the main world were extremely rare, and everything was fine. Now almost any mob is fairly easily replaceable.

Personally I just see this as a waste of resources.

 

...shulkers can be placed in the main world...?

As long as you know where to search, you can find them. I occasionally see a group of horses ~100 blocks away from the border of my town. As long as you are searching in the appropriate biomes, they are replaceable at no expense.

 

p'rhaps we could just offer a replacement spawn egg if a person can provide proper evidence of ownership? a lot easier.

 

I don't think this is feasible, as I could just go around collecting horses which you can find really easily if you know where to look, put name tags on them, get someone to kill them and then get like what 100k worth of spawn eggs as replacement?

As for the whole suggestion, -1 as I see no point to this. As 314 and Nicit said, all mobs are pretty easy to replace if you know where to look. Also if for you having your animals killed is a regular occurrence, just house them in a more secure place, such as a town where only you have perms.

 

we could have a mod spawn them? that way there's no external value, but the mob is still redeemed.

 

What would even be considered proper evidence of ownership? There's nothing I can think of that can't be easily abused.

If you're having issues with your mobs being killed keep them in more secure areas.

 

Keep your mobs in an area where the only way to kill them is to grief. Then file a grief report if someone kills them.

 

I think this would cause more hassle than what its worth. I have to agree with Nicit on this one:

 

Sounds not feasible as you put it, but what if we added a town flag that makes non-hostile mobs impossible to harm but still be interacted with. This could remove a lot of money from the economy from doofy people like me who want my animals milling Bout AND add they ability to make new events like horse racing and public horse towns financially possible.

 

-1, there are far more important suggestions at the moment, and I agree with the above posts.