This one change would have made WW2OL great

The ability to spawn "multi-crewed" infantry squads (9-12 people) and platoons (48 or so) together. Think about logging in to a multi-crewed infantry squad: someone spawns the squad machine gun, the AT/satchel carrier, the leader with an SMG, and 6 or so other infantrymen. And think about running into an opposing infantry squad in-game with all of the exchange of firepower that you would experience. Add to that the ability to coordinate forming a platoon of infantry squads--comprised of 3 or 4 other infantry units--and possessing a platoon AT gun detachment. This certainly would have changed the nature of the game for better, as it would have facilitated a much needed sense of cooperation and togetherness.

As far as overall gameplay is concerned, multi-crewed infantry units could have provided enough backbone for infantry to fend for themselves without a constant need for armored vehicles. The infantry units in turn could have established real lines of defense and attack that would have demarcated the front line from the rest of the battlefield, and it would have given players a real sense of being pitched in a battle against an opposing army.

But I'll grant that small game developers such as CRS probably have a lot on their plate, not the least of which are performance thresholds and connectivity limits, so all of this may not have been possible in the early days of WW2OL's release. But IMO the biggest problem with WW2OL was that it constantly overhyped vehicles without giving enough thought to the imbalance it could create; battles were much too quick and chaotic, and there was rarely ever a sense of cohesion. Remember that even with the vehicles as the mainstay of WW2OL, the "front lines" largely consisted of static WW1 battles for Dutch and French border towns. If infantry were given greater stature within the game, it would have given tanks the reason for which they were originally made: to break through large infantry formations--not to confine single infantry players to a building with a "radio" to be captured or defended.