this is exactely wath the script of Deadclown is doing.
A lot of Vray-specific maps (like VrayDirt or VrayColor etc) are already converted automatically. Not all of them of course since there’s not always a way to convert it to something useful or similar in Corona.
If, however, there is a map that can be converted but is not supported by the Converter I may simply have forgotten to do so and I’m always open for suggestions 
In case you’re not using the latest version (v0.22) I’d recommend to update. If you’re using an old one, don’t change the conversion modes (object selection and material slot selection won’t convert maps).
What red Vray logo?
Basically you can convert everything that you have imported to max, doesn’t matter where it comes from, as long as it has materials applied to it which are supported by the converter.
I had a look at these some time ago but since I did not find any scripting support there is no way I can add it to my converter, sorry.
And what about Maxwell 2 Corona converter ?
I guess this would be harder since MX is using BRDFs…
The Mat Converter will only convert Vray mats if Vray is installed. So i.e. mental ray users won’t be able to convert Vray scenes.
If you dont have Vray installed, do same as I do. Dowload the demo, use all features you are interested in and never render using It