Sure you can use Kontakt like you did in MainStage.
Every Instrument loaded in Kontakt reacts on its own channel, right?
In this example a Midi Keyboard sends on Channel 1 and in each midi in block you can define the channel which sends to Kontakt.
This way you can implement very easy key splits and each split sends on its own channel to Kontakt.
Do you get the idea?
This should be very helpful: