If your question is, "can wind resistance be reduced for everyone on a small circuit," then the answer is "yes, this is a well-known effect, and if the circuit is small enough even one rider is enough."
It is well-known that riders on indoor velodromes create their own "draft" by circling the track. This effect is large when the number of riders is large (for example, in a points race) but is even measurable when there is only one rider on the track (for example, for the hour record). Even a straw can stir up a bath tub, and even a single rider can set up a circulating current in a velodrome. In a typical velodrome the "draft" varies between the straights and the curves, and from the infield up to the top of the banked curve.
The amount of "draft" or aerodynamic benefit varies, as noted, with the number of riders but also their speed. For a single rider on a 250m indoor velodrome at individual pursuit-like speeds the reduction in "effective" drag area due to this effect can be close to .005 m^2.
Field measurements of aerodynamic drag based on velodrome tests must be corrected for this effect. That is, real-time measurements of drag will decrease for the first few minutes while the rider "stirs the bath tub" until it reaches an equilibrium value. You can also see this in the power-to-speed relationship for hour record attempts (which are always done on a track -- power-to-speed decreases over the first several minutes) and in team pursuit events.