CLI interface limitations - workarounds?

I am developping a web player for LMS and there are a number of things i would like to do which do not seem to be possible using the CLI interfaces. As a workaround, so far, i am using the CLI API to obtain all the albums/tracks/artists in my library, which i store in an indexeddb database and use with alasql in javascript. I may have missed something however...

Here is what i would like to do:

- display/search artists by role (album or track artists vs composers vs conductors) and genre. I cannot seem to find any way to get information on the role of an artist aside for compiling all the tracks. This is a pitty, since the LMS SQLite database actually contains a table of artsist by role. Moreover, in the tracks, multiple artists within a role are concatenated with a comma as a seperator, and splitting them up is not very fast.

- display albums with the full artists tag (seems the CLI interface only gets the first one). The full list of artists only seem to be available in the tracks search. Ex: having configured "/" as the separator in my library if i have an album with "Duke Ellington / John Coltrane" as album artist, the albums API only returns "Duke Ellington" in the albumartist..

Any suggestions would be welcome.