The only thing to consider if a germanium diode is to be used as a replacement for the Westector is that a 4volt forward bias is applied across the device.
The bias will not be required for an OA70 or the like.
How about trying out the EA50 or the VR92 thermionic diode? Again, no forward bias will be required.
https://www.radiomuseum.org/tubes/tube_ea50.html
The valve is about the same size as the Westector. A B3G socket will be required which can be difficult to find.
The attached circuit diagram shows how the bias for the Westector is derived.
DFWB.