Hi Nicola,
Nice topic! :-)
I would say that in the longer term this request should be added as a SoapUI O/S feature request - please see:
https://community.smartbear.com/t5/SoapUI-Feature-Requests/idb-p/SoapUIFeatureRequests/tab/most-kudoed
Haven't checked, but I don't think it would be very hard to add the extra methods to support WebDAV - I will vote for the feature request, and would do it if I ever get time!
In the shorter term, the only approach I can think of (and its a little hacky), would require a custom Request Filter to be added to override the HTTP request method to whatever you need e.g. override GET to PROPFIND. This would require a bit of coding which could then be added as a library - as per http://rupertanderson.com/blog/1-how-to-develop-add-and-use-a-custom-groovy-library-in-soapui/ (but with different code!) I can have a go at this if you are interested.
Otherwise, maybe another approach along the same lines would be to use nmrao s nice mechanism for patching in listener scripts https://github.com/nmrao/soapuiExtensions - it's along the same lines, but would require a bit less effort.
Or if the above approaches seem like too much hassle, I understand, ideally we should add in to the standard product as per the feature request! Thanks for reporting the issue anyway.
Regards,
Rupert