Eliminate Thursday? This is a great idea! Although, there might be one or two small drawbacks.
I guess immediately, everyone's annual income is cut by about 8%.
Since Monday's and Friday's have been shown to be less productive than Tuesday, Wednesday, and Thursday, the annual production of the nation will drop by more than 8%. Let's just say 10% total.
Perhaps over time, efficiency will actually improve for reasons of mental health and happiness, as you suggest. But in the immediate time frame, there would definitely be an economic crash prior to any benefit being realized.
Sports teams suffer a rash of injuries to their star players due to physical stress caused by loss of one recovery day between matches, and, as a result, the general level of excellence in professional sports declines. Fans pine for the "good old days".
Sunday papers are now printed 15% more frequently. As a result, paper consumption skyrockets and north and south america are rapidly deforested to keep up with demand. At the same time, landfills quickly fill to capacity with discarded papers. Seeing an opportunity brought on by a lumber shortage for new home construction and the availability of waste paper, a new industry, paper mache home construction, takes off.
Every instance of scheduling software, spread sheet, or other date using application must be re-written, patched, or abandoned and replaced with new software. Airlines, trains, buses, trucks, ships all fail to run on schedule. Companies incur staggering costs to update or replace now useless software. Markets crash. Economies collapse.
15% of TV shows are immediately cancelled as their time slot has vanished. Actors, producers, show runners and writers flood into the only other profession available to them, political commentary and satire. Governments soon collapses under the onslaught of snide commentary and insightful dialog leading to global anarchy.
Enraged by the global decision to drop Thursday - Thor's Day - the Thunder Gods holy day - druids, Norwegians, and closet vikings the world over raise the hue and cry against the affront. Seeing an opportunity presented by the global economic and governmental collapse, the New Viking Union, represented primarily by Norway, Sweden, and Ice Land, sweep in a Second Norse Scourge across Europe and North America. Soon we are all eating lutefisk.
You know, come to think of it, I'm ok with Thursday.