Maybe then give one simple solution..
Use the Realguitar, Guitar Ring 2.. and record each chord root key under wave file...

Define by default the range keys where this all root keys chords have to be played.
Drag&Drop this all files under Gigastudio and create a new GIG file of the Guitar sound type desidered.

For Each chord type ( like Maj, Min, 7th..and so on..) add a new gigastudio Layer switch controlled by Midi CC.

So...for switch chords root keys ( transpose) is really simple, because need only send the new global transpose.

For change Chords Layers we have only to add on qranger code the relatve midi CC number and when a new chord layer is pressed, we send also this new midi CC.
Linuxsampler in realtime will also switch in realtime the chords layers.
Under GIGA format the file can be bigger how much we need, like the Bosendorfer 290, 1800Mb and 16 Layers switch, will preload in cache just in some seconds, or persisten realtime on cache RAM.

the only problem that I see is the BPM change..
IF I will take this way with the GIGA format, we have to include the commercial Zplane.de Elastique plugin engine inside the Linuxsampler GIG too.

I will see if they allow me to include...