Create a TopN DAX measure across multiple columns

Hello,

I am trying to create a series of card dashboards for the top performers in our business across each activity type. I have a fact table set up for each activity type - let's use the example of my 'Client meetings' fact table. Within this table each row contains a date and details of the client meeting, followed by 4 columns with the names of the Consultants who attended the meeting. I would like to create a TopN DAX measure which returns the name of the Consultant with the most meetings - this needs to count the data in all 4 'Consultant' columns, and also be responsive to the date slicers I have on my dashboard page.  In the hypothetical example below the result I want is "Miss Peacock". In the event of a draw I should like to return 2 names. 

For another TopN measure I would also like to be able to include additional criteria such as Consultant who has attended most meetings which are 'Cross Practice', so adding in a filter for "Y" on the 'Cross Practice' column. 

I hope someone can help.

Thank you

Quenril