Does anyone know if it's possible to create an injected nsps that can run multidisc saturn games (Panzer Dragoon Saga, Deep Fear, Enemy Zero, etc)?
Yes it's possible to have three games with the Saturn Tribute compilation but it's very technical to make it automaticaly. To do it the NSP should be rebuilt with modified NCAs containing the games/texture.tex/PlayingGuide/etc... The NSP compilation is a NSP that contains each NSP of each game and an additional application to launch the wanted game, it's a simplified explanation of how the NSP of the compilation is built. So yes it's possible to do a multi-disk game with the compilation but you can only use three disks and I don't think that I will implement this in my script cause it's to mutch work to do and I don't have the time to do it.
For those who want the logic to do this (the process could be wrong because I've never tested it) you should extract the NCAs of the NSP of the compilation, find the NCAs containing the games and extract them in a separated folder for each one, delete the NCAs containing the games, replace the content wanted in each folder, modify the TitleID, name of the game, author, etc... of the "control.nacp" and "main.npdm" of each NCA of the compilation (to do that you should extract the content of each NCA, delete the NCA extracted, modify the files and rebuild the NCA) and finaly rebuild the NSP with all the NCA replaced. A thing that I don't know is if the file containing the infos on the structure of the NSP should be modified or if it could be automaticaly created during the rebuild process with Hacpack.
An other possibility is to modify the TitleID of the NSP of the compilation (the name, author, etc... could probably be modified also), install it and use the layeredfs method to replace the game files, this use more space on the SD and on the target where the NSP is installed but it's probably more easy to do like that.
To help to understand I will attach the cnmt of the four NSP, for the NSP of an unic game we can simplify the structure but for the compilation it seems more difficult to do that.