Yes you cannot modify the design of this list page. Dashboard & custom html webresource/iframe is fine.
But I recommend you to customize this list page itself to look like what you want, atleast close to similar CRM UX. First deactivate all the views for that particular entity except Active & Quick find. Rename the system view “Active Details” into “Search” & modify the filter condition to include something like createdon = tomorrow
. Hence the grid will be empty, you got search box on right to start with. When user search, Quick find view resultset will be rendered in grid.