Why can't you run portable apps on RT? Nothing is being installed to the system. It's all either, on the USB flash drive, or in a folder. You don't have to install anything. So, why can't you run
How do I get my apps to see the files on my removable drive, such as USB, network drive, or SD card?
Resolves an issue in which NTFS permissions for removable or external media could be bypassed by using certain tools.
Find out how to use the Music app to buy or stream songs and albums, or rip music from a CD.
Fixes an issue in which a USB 3.0 Bluetooth device that is connected to a Windows RT 8.1 or Windows 8.1-based computer still drains power when the computer is in sleep mode.