Rod,
I can't speak for everyone.
What do you propose that isn't vendor specific?
There was some talk about
http://en.wikipedia.org/wiki/Dynamic_Multipoint_Virtual_Private_Network
And there seems to be an open source compatibility here:
http://sourceforge.net/projects/opennhrp/
I'd be willing to dabble with this, if someone else wants to.
The common point of presence idea, might make things simpler, but then
that is a possible point of failure.