This is the real answer, though keep in mind this folder name depends on what you called it with Frosty.
I left as default, so in my case the folder was named "default" instead.
I put the path similar to yours replacing "mods" with "default", and it allowed me to launch it straight from the Origin client.
I have Battlefront 2 set up in a specific way for mods now; Frosty should just be used for adding/removing mods or changing the order, but after the testing is done I prefer launching it straight through the client.
It's quicker, and it can help resolve issues when mods don't display correctly (something about the cached content not working as it should through Frosty compared to running with the Datapath argument instead).