I think this is doable with the j2eeserver module 
and it would help with weird errors. 

Take a web module and make a filter declaration in 
the deployment descriptor but don't add the class 
(for example). This will prevent the module from 
starting. 

If you try to execute a JSP from the module, you 
will see that the resource is not available (and 
the monitor reports a 404 because it gets started 
even though the module isn't, which is kind of 
weird if the settings are supposed to be inherited 
by the individual modules!). 

The server registry will report that the module is 
running too, unless you do refresh. 

It would be really nice if we could provide a 
helpful message that the module failed to start.
Feel free to set this to be An RFE.