Is there any interest in a "policy_composite" library which will have policies just as the proposed policy_ptr: http://cvs.sourceforge.net/viewcvs.py/boost-sandbox/boost-sandbox/boost/poli... library has policies? These composite policies might allow different allocation strategies for variant and possibly different CTOR arguments for tuple. It could also allow adding different methods, such as the get_base_ptr(void) as described here: http://groups-beta.google.com/group/comp.std.c++/msg/27e41e693228c6c7?hl=en& which would of course satisfy (hopefully) that OP's request for a variant extension.