I have tried the tactic
"What if British will make D-Day 22 June, 1941?"
The result (after 10 days of fighting) is following:
1) All north France (including Paris) is in British hands. Full liberation of France sees no major obstacles.
2) Heavy fighting on the coasts of Belgium and Netherlands
3) Gibraltar is lost
4) Malta has fended off the initial French/Italian assault, but losses are dire. Most capable bomber force was evacuated to Alexandria
5) A major defeat of British forces in Libya. Retreat to Cairo may be considered, as positions in Alexandria has potential to become a trap.
6) Stalemate in Syria - British has air and sea superiority, but not enough ground forces to immediately crush Vichy`s French forces.
7) Reunion island captured, British forces are landing in Magadaskar
8) Shelling and capture of French and Portugese colonies around Africa
9) Forces concentrate in Persian Gulf to attack Iran.
10) Portuguese Goa in India was captured by British forces
11) Burma forces are fending off the Thai assault, no problems predicted
12) Singapore is safe, In British Malaya a force to conquest Thai is being gathered.
13) Heavy fighting at approaches to Hong-Kong. British reinforcements do arrive from Brunei, but it is not known if Hong-Kong can be held continuously.
14) Pre-war stocks of ammunition are depleted (at least 1 sort of heavy weaponry is given to approximately 100 new divisions, another 100 divisions are without equipment)
15) Production of light weapons do rise, but can not rise production speed of all weapons simultaneously. Heavy guns and aircraft production is particularly stalling.
16) Few bugs were uncovered and fixed (see viewtopic.php?f=2&t=625&p=5419#p5419 )