Given Meteor's support for eventually-consistent offline writes to data objects, automatically merging concurrent edits to the same text field seems like a natural next step. This might be done by integrating some of all of an operational transformation library (list) such as ShareJS.
Is there a desire in the Meteor team to support this functionality in the core product at some point, or would it more likely appear as a third-party add-on module?
Also, since ShareJS actually seems to provide the basic functionality of the Meteor data architecture (they mention in their documentation that it works with arbitrary JSON objects), would it perhaps be possible to do something like Meteor using ShareJS for data syncronization?
I'm guessing it might be something they might add or could be done with packages.
In the meantime however: You could use Meteor.methods to expose an api to communicate to the same field back and forth. The method could do a diff on the change and merge it to the Collection before returning what should be changed on the clients computer.