Just an idea for the next version: you could externalize the music tracks in MAPINFO to the LANGUAGE lump, so that other people can make their own mix of them (Aubrey's bonus tracks are coming soon, so I know I will), especially for the Retribution episode and bonus maps.
Another thing, I noticed that BIGFONT's red colors are a little off compared to the one that appears on graphic patches like CWILV. Tt can be very noticeable if, for example, you change the menu and place the patches next to generated text.
To fix this, you can use the TEXTCOLO lump and add the following:
Finally, I also noticed that you're adding the "Doom 64 features menu" by rewriting the whole default options menu, which can cause conflicts with other mods or newer versions of GZDoom that add more items there. You could use AddOptionsMenu instead to preserve the default menu and only add your new items.
That's it, I've been enjoying the mod a lot! I eagearly wait for the Retribution and Outcast episodes,