Moin,
You will need some sort of MIDI processor, that is able to read MIDI messages, process/change them and put them out.
This may be a computer software (try to get Your hands on e.g. Ableton lite, if You can live with a "real" computer), a special hardware like the "Sipario" by Lab4Music, or something You will find cheaper and easier.
The trick in Your case is to connect the MIDI processor to P08 MIDI out and to program it to convert different MIDI keypresses to different MIDI channels. These may or may not feature a gap, overlap in parts or total, or whatever You want.
In live situations I use VIP (a software by In-music I got for free with a cheap AKAI keyboard) to control VSTs, which allows me to define "Multis" with up to 8 VSTs, that can react on independent keyboard regions.
Ableton - even lite - is able to route from and to external MIDI using cheap USB/MIDI interfaces. Meanwhile I use the full Version for recording/production, maybe will use it live in the future...
But I know and have talked to people not wanting to use computers (a few Years ago I was one of them...). They use MIDI controller keyboards and expanders only, one is happy with the Sipario as centre of his MIDI-setup. This machine not only routes very flexible, but also has programmable scenes, that may change the MIDI-routing fast and easy in live contexts. Not cheap however...
Chances are, that cheaper things less flexible but sufficient for You will exist.
HTH
Martin