But I must admit I wonder why the OPL family was chosen, because for example the YM2203 is AY-3-8910 compatible while adding FM channels to it. Then again, that chip was probably avoided due to its association with NEC's PC88 computers.
Interesting thought, and a plausible theory.
Actually, I'm glad it went that way. Just compare the sound of games like Dragonslayer VI, Fire Hawk, Starship Rendezvous, Valis II etc. with their PC88 counterparts, and I think it's pretty clear who wins. 
As I am used to Commodore 64 original, exploding enemy sound effect feel somewhat odd, I was hoping it could be changed to samelike what Commodore original had. Exploding effects do sound clearly usual msx-style, not like the original version, but I can live with that. (Unless you can still modify them for cartridge release?
)
In the latest video enemy ships now have black outline, does they have three colours, which is only visible on real machine? Enemies now look a bit like what was used in some japanese msx shooter or Spectrum port with added sprites. Yeah, I am also used to the sprite colours of Commodore 64 original. As it was said game will have 64 sprites maximum, I thought enemies might have same colours as on Commodore. Please do not get me wrong, I am very happy for your efforts, guys! Most MSX´ers probably won´t see or hear anything "wrong", I just happened to play this decades ago on Commodore and I do still remember how it sounded and looked like. And I have pre-ordered the game already.
[edited] Yes, I do understand, black outlines will most probably make enemies look more clear against backgrounds. Two colour enemies without black outline might get a bit lost against some colours.