NAT Real Server >> VServer

Your request seems a bit convoluted. I can understand what you are trying to achieve but why do you want it ? If the reason is provided, may be an easier solution can be offered by someone in devcentral.

Possible Solution:

VS-1:Server-1 VS-2:Server-2

Both VS-1 & VS-2 can use SNAT automap. In this case, client IP will remain the same as seen by Server-1 & Server-2. There can't be more than 65K connections via the VS, assuming you have 1 self IP and no floating IP.