as it is we have to settle on whatever textures appear in the assets as set by kubejs if kubejs assets are added..
example:
a mod which adds heart or armour icons needs some icons added.
it would be great if we could add 16x16 suggested default assets with kjs, leaving the player to decide if they want to use these.
forcing a player to use these without option to override with a resource pack means if they wish to use a higher resolution resource pack they're going to have to just deal with the fact that their armour/hearts icons are still 16x16 textures.
(kjs used to load assets in a different order so this wasn't a problems before that)

pls consider adding this option then add it.
i do use 1.16.5 because i'm working on a modpack that restricts me to that version but i seriously think that even if you only implement this into latest builds it would be a boon to the community at large.

I think the better suggestion here is, let dedicated filesystem resourcepacks be stronger than KubeJS. KubeJS assets folder will always override textures and other files, so you can easily modify mod assets. Imo if you make user pick and move files around or have them set some config, thats not good pack design. Instead I recommend you ship a resourcepack with your modpack, and then they can use minecraft's mechanics to enable or disable them. But since KubeJS currently overrides filesystem resourcepacks as well, this is a valid suggestion, just title needs to be "Resourcepacks should override KubeJS assets"