Thanks, it works and it works good ! Tried it on quite a heavy scene and it worked pretty well.
Now it would be even better if anyone could do some kind of script which not only converts vray proxies but also can kind of relink those which are already used in multiscatter/multipainter (for example) thus keeping their position, scale, variation etc. of course, common sense is telling me that should be possible to do only on multiscatter developers side - inside the plugin itself or maybe it already got such function but I just simply overlooked it (it does happen sometimes :) ) and if there is such a thing someone please elaborate me.
For now I found comparably easy method by using Generate Objects in the MultiScatterTools , deleting original Ms helper/gizmo after that and then running your script - thus, even if loosing Ms objects themselves :( one can quite easily convert some vegetation heavy vray done exterior scene in no time, if not for material tweaking afterwards of course.
Thanks again !