What do you mean by speed rendering? If the sim is running at 30-60 fps, do the objects not move by and change perspective as they should?
I think I understand what you mean by things seeming slow...but, I have always attributed this to less detail in the simulator environment (grass, ground texture, etc.) to give the impression of movement.
The FM should absolutely be improved...It's ridiculous to say a good flight model is impossible. Maybe floaty and rail-ey are the best you can expect in FSX, but we know what DCS is capable of.
I also remember Polychop mentioning using a third party software system for their FM. I wonder if this has much to do with the limitations we are hoping to see improved...