Switching selection in a multiselect dropdown from all to the one user is hovering on

I am designing a dropdown menu in a report generation UI where the user has the option to select the seller he want's to see the report for. The control defaults to all sellers selected for the report. On clicking into the control, the user is presented with multi-select checkboxes with the option to toggle between all or none at the top. I am trying to explore a solution where a user is able to switch from all options are selected (which needs to be the default state)to selecting only one (without to need for the user to click 'none' and then proceed with checking the selection he needs to). Here is what I was thinking: 1) On hover over any row that the user wants to select, show the text 'only' 2) If the user clicks on the text 'only' all other checked items will be unchecked and only the selected one will be checked 3) If the user clicks anywhere else on the row, it will toggle the selection

My question is: 1) Is it bad to have two clickable elements on the row in a multi-select menu? 2) Does this appear to be intuitive? 3) Any other suggestions as to how to achieve the result I want.

Please see the image below to get an idea of what I am trying to do. Thanks much]1