vagfilm
Simply adjusting the overall velocity curve does not solve the problem, if different curves at bass, mid and treble octaves are indeed needed as @johanibraaten and @MalcolmH mention; therefore, the need for VelPro.
I have a tool that I programmed that can do velocity curve mapping per key, but it is not user friendly at this moment because it is simply for my own use: you need to create on excel a matrix of 88 velocity curves. It is not difficult but gets quite tedious. I want to make a simple interpolation tool that automatically creates those gradients, but time is in short supply. The good news is that it is free and it seemingly does not add latency (this needs third party checking), but it is Windows only. You only need a virtual port to output the midi out-value to the VST.
Let me know if this is of interest...