I hope all the hardware is still in good working order, or at least easy fixable. Are you going to keep the scene updated 
?
So, everything is just working as Poltergeist described, even the floppy disk drives (guess those models have no belts) The keyboard contacts will just need some clean up, not a problem (I'll maybe try the girlfriend's stockings method for the keys you described :))
The MoonSound sounds great (I was afraid of some capacitors issue like on my GFX9000, same manufacturer, same age).
I was quite surprised by the "woofing" sound that the Sony G900AP makes at boot time. It vanishes just when the MSX logo is displayed, I guess that's because of the audio and video mixing capabilities? My project for this machine is to modify LaserDisc game loaders to launch those games on my PiLD thingie (also finish that project and make it public).
I'll keep the MSX2+ modified VG-8235, maybe replace the frame with a bit better looking one (well, not that I do not really like the new paint job... ok, I don't like it :P), and the disk drive with a black model.
Hamlet, I've checked what I do not need and what will remain after swapping / replacing some parts. I have this for your association:
- 1 VG8235. Working, with cables, but probably with a repainted frame that you'll like... (or not).
- 1 Philips monitor
- 2 Philips MSX mices
- 1 256KB expanded music module
- 1 FM Stereo PAK with a new cartridge casing (you'll just need to drill holes for the jack plugs).
- 1 Sony trackball
- 1 joypad.
Even so somehow a pleasure trip don't you think? Taking into account the great stuff you picked up of course! 
That sure was, somehow giving me the feeling to deserve that little treasure. I had to stop at a highway station after leaving John's home just to have a look at everything for a while, like a little kid (I also re-arranged the MSX machines on the back seats instead of the box, I was a bit afraid of the vibration effects during a long ride).
Ok, here's a little report on what happened to Poltergeist's hardware legacy!
First, about the Sony HB-G900AP, that machine was in great condition. I just dusted it and add an extra B: drive on it (I discovered that one of my spare drive here was exactly the same model as the A: default one on that machine, just with a different color!):
One of the curious thing with that HB-G900AP is that the disk drives have priority above MegaFlashROM or other mass storage devices inserted in external slots, so the disk drives are always A: or B:, just like on PC!
There were some black gummy-strains on the keyboard, which went away easily using some white-spirit and Q-tips. It now looks perfect:
That machine is now in my play room, connected to a Gouda slot expander, but will move to the "development desk" soon as I have some projects for it:
About the fancy-looking 256KB MSX2+ expanded VG-8235, I decided to move the main board to the other original VG-8235 (here with a Rookie Drive):
I drilled a hole in the frame for the switch allowing to choose MSX2+ or MSX2 BIOS:
That's a great machine, and an original configuration I did not had for my tests before.
Finally, I built a VG-8235 for Hamlet using the remaining parts of Poltergeist's original VG-8235 and what I have here. That worked great, but the power supply I took from Poltergeist's machine just died when testing it (the fuse was exploded, with lots of glass debris inside the power supply).
Anyway, I had another power-supply in stock (and also a German keyboard). So here's a part of what will go to Hamlet:
I reflashed the BIOS to German, and had to built and adapter for the double-sided drive following Jipe's instructions (plugging it on the B: plug on the back side did not work on this model).
The blue cartridge is the FM-Stereo PAK from Poltergeist. I cleaned it with white spirit and glued it firmly, and it works great.
I maybe still have enough parts to make something with the remaining repainted VG-8235 chassis (which is for now just empty ;():
