My answer to the tactical goalkeeper "injury" problem.
If a goalkeeper goes down injured and play is stopped, all the outfield players have to stand on the touch line on the opposite side of the pitch from the management and training staff. Any outfield player interaction with the non-playing staff is an immediate red card. That would sort it.
For what it's worth, I'd apply the same rule during cooling breaks. The players can pick up drinks / gels etc. left out for them on the opposite side of the pitch, but not interaction with the coaching staff allowed.