nLoader does only support a small subset of TI-Nspire CX production OSes and has no boot menu
It's just that the exploit is inferior (Boot1.5 instead of Boot1), making the environment much more restrictive.
Also, I don't think you have to remove nBoot+ControlX.
Just don't alter the Diags partition, and put in the Boot2 partition :
- Boot1.5 4.4
And then tell ControlX to boot Boot2/Boot1.5 4.4.
If it doesn't work, you'll just have to tell ControlX to boot your ExtnD/Boot2 4.0.3.