I hope it's okay to cross-post this, as I posted it yesterday to the Effects form as well.
I just a released a fairly simple but powerful little plugin that allows you to redirect and modify MIDI messages by applying custom response curves. The plugin can be downloaded directly from the product page. The product page also includes some more detailed instructions on how to use the plugin. The source can also be found on github, which may be of more interest in this forum.
To use the plugin, you just place it somewhere in your FX chain and select a MIDI input source from the top-left dropdown, as well as a MIDI output destination from the top-right dropdown. Then you can modify the curve graphically and observe the effects. During playback, the GUI will show incoming values and how they are being transformed, as shown in the second screenshot below. The plugin can be chained as well in order to affect multiple types of MIDI messages in a single FX chain.
Hopefully some of you will find this plugin useful. Feedback is more than welcome!
Screenshots
General usage screenshot, showing a curve that will use velocity values to modify pitch bend:
Highlighting how the GUI displays the last received MIDI input in real-time:
