Using the PIV applet as smart card is not easy (typically, read only) and the OpenPGP applet is not here to store many certificates but only one and cannot be integrated as a read/write card.
As an alternative, the GIDS minidriver is natively present in Windows since Windows 7 and will be supported soon by OpenSC.
That makes a read/write card.
Are you considering supporting the GIDS applet (see links bellow) in addition to the 2 previous applets ?
https://msdn.microsoft.com/en-us/library/windows/hardware/dn642100(v=vs.85).aspxhttp://www.mysmartlogon.com/generic-identity-device-specification-gids-smart-card/https://github.com/vletoux/GidsApplet