Fuzzy Logic did implement caching in their f-kernel. So it is possible on MSX. @ro how did you do that?
Oh, that...
Midas, our OS - also known as F-kernel -, uses a pre-emptive "caching" system. It's not bound to disk actions. It's a combo of RAMdisk / Cache kinda thing. It shines when using the included File-Retrieval-List (FRL) module, where previous loaded files will not be loaded again (expect if they're forced to load).
And, yeah, it would very well work on a game like this.
Funny detail, I've been refactoring the whole darn f-kernel last year and made some big improvements. It won't be long untill you will see this for yourself; I've planned something within the very near future to be (re) released 
/ offtopic
@SjaaQ: Well, that's kind of a large decision then. Even in the synth world it took quite a while before (some) ROM-samples became stereo, and those machines had been using megabytes rather than 512 kb. 
And these synths were often limited to a few specific instruments like a piano.
When I'm prepping a wavekit I need to force myself using anything over 22kHz when a sound needs it - and I rather try to work around it. Let alone choosing stereo. 
@SjaaQ: Well, that's kind of a large decision then. Even in the synth world it took quite a while before (some) ROM-samples became stereo, and those machines had been using megabytes rather than 512 kb. And these synths were often limited to a few specific instruments like a piano.
When I'm prepping a wavekit I need to force myself using anything over 22kHz when a sound needs it - and I rather try to work around it. Let alone choosing stereo.
The only decision we had to make is how many SRAM the audio guy was allowed to use. And that was just to keep loading times down. After that he could do what ever he wanted.