Here is an updated version that supports file extensions. It will still use /documents/ndless/phoenix.raw.zip.tns if it is launched directly.
And it has a theoretical CX support, but launching official OSes still fails.

SilverOne on TI-Planet has discovered that launching any OSes < 3.1.0 will work when OSLauncher is in the ndless/startup folder, so launching CAS OSes on non-CAS devices should be reliable now (link, but the menus will be messed up). Sadly, this method doesn't work on CX calcs (tested in emulator).

Well, it was Excales idea  so i can't take all the credit ^^.

What do you mean by file extensions support ?