proposal: nodes as parameters

Good day!
I am using the libxslt wrappings more and more seriously, and I am 
running into problems with some limitations of the API. In some cases, 
I would like to contribute work, but first I would check that such work 
would be welcomed into the codebase.

My primary issue is with parameters to stylesheets. In the current 
implementation, (libxslt.c 1.25;L469) you check explicitly that all 
parameters passed from Python are strings. I am interested in actually 
passing nodes or nodesets between stylesheets through parameters. (Is 
this allowed by the C API at all? I did not check on that side yet.)
Is this something that you would consider harmful or useful? (i.e. 
should I plan to work on this or on workarounds?)

Also, I saw that there is no convenient way for me, as of yet, to 
return an error from a Python function. This is actually marked as a 
TODO item in the code, I could give it some time if I am told nobody 
else is actively working on it. But I am new to C-Python interaction, 
so someone should check my code.

Marc-Antoine