As anyone who has been using this add-on may have realized, the current (3.2.0 Beta), now shows an error within the launcher. It reads:
"You are running an old version of the launcher. Please consider using the new launcher which will improve the performance of both launcher and game."
For the time being, this error should just be ignored. Minecraft should continue functioning as usual. As soon as I figure out a way to run the new launcher in a portable fashion (if even possible), I will release a new build with support for it.
As always, please report any bugs in the comments.
Edit: For the time being, it does not appear I will be able to use the new launcher along with MCPLA. The new launcher does things differently, such as auto installing a build of Java, including an installer, and use of the Program Files directory. The "old version of the launcher" seems to continue to function properly. If you have problems with installing certain builds on Minecraft, I recommend deleting the contents of the ".minecraft" directory on your portable device. Doing so will allow a fresh copy of everything to be downloaded. Be sure to backup anything you want to save beforehand! :)
Thanks.