KeyStage, from Ali Gokturk, was updated with a bunch of new MIDI routing options, with MIDI aliases!
What's new in KeyStage v1.5:• Input aliases can now have multiple actual MIDI inputs, with additional routing and filtering options
• Each actual MIDI input in an input alias can be routed through a chain of custom translators
• You can also add custom translators to output aliases
• Custom translators now have channel conditions and channel translation options.
• Additional minor tweaks and bugfixes
Here's a new tutorial showing off the MIDI routing from Ali Gokturk's YouTube channel.