The launcher and usbnetwork are totally unrelated. You can install and use
usbnetwork on a jailbroken 5.3.2 without any problem - I've done it.
You can boot into an (SSH-enabled) diags using either "idme -d --bootmode diags" from main, or via mfgtool/imx_usb_loader, or via fastboot, or via ENABLE_DIAGS if you installed the
rescue pack (you need to extract and repackage it for the touch first, but that's about it).
You can downgrade using the normal procedure to flash main partition/kernel. I've done it.
Bottom line: you have tons of options, all of which are working pretty much exactly as on 5.1.2.