For battle scene textures... these days everyone is distributing PNG files to go with Aali driver/ 7th heaven. These files are formatted STAGE##_T##_00.png. They have to be turned into tex and packed into battle.lgp to work with the Switch. Using Iran Textool will convert them to TEX files of the same name with no file extension. Dropping those into your battle.lgp will not work though, because the game has the filenames encoded alphabetically, starting from the file name "ohac".
I couldn't find a tool to rename the resulting TEX files to the alphabetical codes, so I generated a batch file from excel to do it for me. It is set up assuming you are using the program ULGP to pack the files into battle.lgp for use in the Switch version. Here's instructions for converting PNG files and adding the results to battle.lgp using this batch file;
1. Find a directory, stick ULGP there, this rename.txt I've attached, the battle.lgp file you want to add to, and an empty folder "battle"
2. Run Textool, in the upper section named "battle" use the source selection box to select all the PNG you want.
3. Select the destination directory as your battle folder, choose import tex from png
4. Rename (heh) rename.txt to rename.bat and run it. This will change all the STAGE##_T##_00 un-labeled TEX files in the battle folder to 4-letter alphabetical code.
5. go to command prompt, get to that folder, and type "ulgp battle", this will add all files in battle folder into battle.lgp
6. copy battle.lgp to workingdir/data/battle on your switch
As mentioned there's stricter memory limits on the Switch so don't expect the bigger texture packs to work without resizing them first! I used flexxi for a quick, open source batch resizer for PNG. It lets you easily set a max width and height and keep the aspect ratio. There's probably some better quality programs out there though. 512x512 max is working for me so far but you might be able to push it further.