C4R with multiple firms in same model

[GREMMELS1]

We currently allow our structural consultant to work in the same Revit model as us on C4R/BIM360.

Is anyone else using C4R to house multiple consultants within the same model? 

How would you change your process if you had another design architect on board that was in charge of ID drawings?  

We allow our Structural Consultant into the same file because we work with them on 90% of our projects and trust them to communicate changes to us and not to screw up the model.  If the model does get screwed up there is a general understanding that those things happen and that we will work together to resolve the issue.  But not sure where to draw the line when it comes to letting other firms into the same file that you haven't worked with before.  In our case, we have another architectural firm that is going to be responsible for ID drawings, so I am trying to think if there is any reason from a modeling and documentation standpoint that they would need to be in the same model. 

For instance, we might be responsible for certain restroom accessories.  If I place a mirror on the wall that does not include a tile finish and then the ID firm comes through and puts tile on restroom walls it will cover up the mirror.  If the ID firm is responsible for placing a mirror on the wall but there is no tile finish so they have to host it to our stud and gb wall then it can't be hosted to the wall from our linked model.  These are the type of overlap issues that I see happening with having the architect of record and interior architect in two different models.

[GREMMELS1]

I agree from a liability standpoint it isn't ideal to have people in the same model.  I really wish there was a better way to control worksets so that you could assign multiple people from firm A and firm B to control their own respective worksets.  This would remove many liability concerns.  Having separate models linked in is the most common method of practice but also comes with its own set of problems.  For example:

1.How does the ID firm model wall finishes in each room?  it would require them to modify the boundary of each wall where there is a door opening or window opening. When we change the location of a door the ID firm will have to go back and update the boundary, again manually in elevation. 

2. How does the ID firm host accessories to walls that are located in a separate model?  Does that firm now have to modify all their wall hosted families to be non hosted families? 

3. Structural model shows a concrete core but architectural can't put a door in a wall from a linked model.  Structural has to modify the wall boundary to show an opening.  Architectural has to draw a fake wall in the wall opening and then place door in fake wall.

4. Structural floors are modeled with shaft wall openings in them.  Architectural copy monitors floor.  Floor openings don't show up because shaft openings don't get copy monitored.  Structural has to delete shaft opening and draw a floor opening on every floor in the same spot.

5.  In Navisworks you get hundreds of warning that are non issues.  Ex. A duct passes through a full height wall in a linked model. You would get much more accurate clash detection with everything in the same model.

Could keep going with this list but will stop there. I know its not impossible to link models like you suggest, obviously this is how people have always done it.  But to a certain extent it limits the level of coordination and ease of operation.

I am curious how do firms deal with these issues that are a result of linking models?  Particularly questions 1 and 2.