Do not invade Finland instead use the time from when the M-R pact is signed and until Germany invades France to make a thorough plan and thorough preparations for capturing the Romanian oilfields. That operation is to start one week after Germany invades France.
For anyone who does not know about the importance of Romanian oil, here are Hitlers own words, recorded by the Finns when Hitler went to Finland in 1942:
“I always feared - that Russia suddenly would attack Romania in the late fall - and occupy the petroleum wells, and we would have not been ready in the late fall of 1940. If Russia indeed had taken Romanian petroleum wells, than Germany would have been lost. It would have required - just 60 Russian divisions to handle that matter.
In Romania we had of course - at that time - no major units. The Romanian government had turned to us only recently - and what we did have there was laughable. They only had to occupy the petroleum wells. Of course, with our weapons I could not start a, war in September or October. That was out of the question. Naturally, the transfer to the east wasn't that far advanced yet. Of course, the units first had to reconsolidate in the west. First the armaments had to be taken care of because we too had - yes, we also had losses in our campaign in the west. It would have been impossible to attack - before the spring of 19, 41. And if the Russians at that time - in the fall of 1940 - had occupied Romania - taken the petroleum wells, then we would have been, helpless in 1941.
Another Voice In Background: Without petroleum...
Hitler: (Interrupting) We had huge German production: however, the demands of the air force, our Panzer divisions - they are really huge. It is level of consumption that surpasses the imagination. And without the addition of four to five million tons of Romanian petroleum, we could not have fought the war - and would have had to let it be - and that was my big worry. ”
End of the quote
These things should also be done when one invade Romania:
Stop all exports to Germany when the invasion of Romania starts.
Contact Germany and say that the exports can restart but that first Germany has to pay for what has already been delivered from the USSR, Germany was lagging in payment.
If the Germans pay what they owe, say that the Germans must pay in advance for the next set of exports. If the Germans pay, keep the money and send nothing. Thereby increasing the strain on the German economy.
The seizing of the Romanian oil wells should create an economic collapse in Germany, the cancellation of the grain exports from the USSR should create huge food shortages.
And by being paid in advance by the Germans for things that will not be supplied, that will crate even more pressure on an already damaged economy.