Most students will use their English over the telephone, and using a foreign language over the telephone is so much harder than face-to-face, as body language and gesticulation cannot be seen or utilised (you should try listening to me speak to my Mexican father-in-law!) and yet most speaking activities are undertaken face to face.
There are two ways to get round this, using the same example activity. Get hold of a lego set (every language school should have one!) and put students in two groups in different corners of the classroom, or in different classes if you have the room. They must construct something using the lego, preferably something abstract. Give them a couple of minutes only. Then one student from each group must meet in the middle, put on blindfolds and give instructions about a small part of what they have constructed to the other student, who listens, but doesn't take notes (obviously!) for example, "Get two blue rectangles and put a square red block in the middle". The other student then reciprocates and returns to the group and sets about following the instructions given in the middle, while the second pair meet in the middle and give other instructions, whilst blindfolded.
What then happens is that each group must try to follow the instructions of the other group exactly to form a clone of the lego shape created by the other group. Your role is simply to monitor and take notes on language errors and on expressions that would come in useful, but which they might not need to use when talking face to face (many prepositions of place can be demonstrated when face to face).
If you don't have blindfolds, or believe your Swiss-German business executives might object to the idea of using them, simply place them opposite each other and make them give the instructions over their shoulders so they can't see their opposite number.