I wouldn't say that the Germans would be able to advance further in 1940 than IOTL 1941, but they might just be able to complete the primary objective of Barbarossa, which was to destroy the Red Army as a functional fighting force close to the German border. I imagine that Stalin would order a preemptive advance into Poland which would be countered by the Wehrmacht units returning from the Western front in what would be in practice the second phase of the Schlieffen Plan.
If offensive operations against the Wehrmacht went bad IOTL in 1941 Western Russia, I imagine they'd go worse so far into German occupied territory. OTOH, there won't be any logistical preparations for a counter-offensive into Russia, so anything after 1940 depends on how successful the Germans are of encircling an overextended Red Army, or how quick the Red Army can advance into Germany to make the situation untenable for the Axis.
I find that the Germans have the most to gain in this scenario if they can take advantage of Soviet deficiencies.
I don't agree.
1. Wehrmacht in June 1940 was much weaker than a year later. In the campaign for the West Germans used 7 378 guns, 2 445 tanks, 638 aircraft and 3 350 000 troops. Their losses amounted to 1 236 aircraft, 795 tanks and 27 000 dead. In June 1941, they had a total (together with the forces of Romania, Finland, Hungary and Italy) 4 733 990 troops, 12 686 guns and mortars, and 2,937 aircraft.
2. In the western military districts of the USSR in June 1941 was about 2.6-2.9 million soldiers, but the Soviets were able to mobilize a much larger force. In 1941 they mobilized 5 million people. They could have a very big advantage over the Germans.
3. The production capacity of the Soviet industries were much higher than the German. In 1940, it produced more than 10,000 aircraft. In 1941 - the 12,400. In the first half of 1941, Germany produced 1,621 tanks and assault guns. In 1942, German industry produced 14 700 aircraft, 6,189 tanks and assault guns, 14,300 medium and heavy guns and 9780 mortars. For comparison, in 1941 the Soviets produced 15 735 aircraft, 6590 tanks and 15900 guns and in 1942: 25 436 aircraft, 24 446 tanks and more than 33 000 guns. Industrial production in the USSR increased despite the loss of an area inhabited before the war by 40% of its population. If this did not happen, to increase even more.
4. Germany from June 1940 could not benefit from mineral resources and agricultural USSR.
5. USSR could use some force Romania - the main supplier of crude oil for Germany to introduce an embargo on it, or take the country by force of arms. Lack of fuel significantly limit the usefulness of German tanks and aircraft.
6. Big losses suffered by the Red Army were the result of not only the command of errors and poor quality of the officer corps, but also the surprise effect and the lack of a ready plan of defense. Many Soviet aircraft were destroyed by the Luftwaffe still at airports. In this scenario, the situation is reversed: the Germans are surprised and have to fight without a plan. In the first weeks campaign probably will suffer heavy losses.
7. Even if the Germans found out about concentration Soviet troops near the border in the spring of 1940 that they could not do much because the shifting of some divisions from the western front, greatly reduced the chances of their victory over the Allies.
The fate of the war on the Eastern Front decided outnumbered and material USSR. Germany, so long resisted because in '41 it temporarily reduced the. When the Soviets cool off after a disaster and rebuild his army nothing was able to stop them. The time works for Stalin.