Change player in KMC

You can't use an HTML5 player, because you can't load (complicated) HTML inside flash.
Assuming you want to change the player for the entire installation (you can't change it for a specific partner), you should change the contents of the file pointed here:

or change the pointing, of course.
This uiconf is created at deployment time, so you should re-run KMC deployment script after changing the file contents.
Alternatively, if you only want to change it for a version that is already deployed you can find the uiconf with this name or tag in the DB or testme console, and edit it directly.