Solder Mask Opening for PTH Vias

Instead to have a check box for the option "Do not tend via" in Pcbnew->File->Plot, is it possible to define the value of the solder mask clearance around via hole in order to have partially tented via (solder mask covered < partially tent a via < full solder mask opening). Some PCB manufacturers prefer a mask swell around the hole rather than closing it completely. For example, this could be define in menu Pcbnew->Dimensions like Pads Mask Clearance.
see http://www.we-online.fr/web/en/index.php/show/media/04_leiterplatte/2012_2/dg_poster_1/120102_Design_Guide_Basic_Poster_A2.pdf and http://techdocs.altium.com/display/ADRR/PCB_Dlg-SolderMaskExpansionRule_Frame%28%28Solder+Mask+Expansion%29%29_AD