Multihoming - Resilience or Independence

Hi,
It seems multihoming discussion is an example of vicious circle (sp): More
specific routes result in larger routing table but we want those routes and
small table... Let me suggest a blasphemy: CIDR being advertised from two
ASes. They say it should be only one, but why? In my opinion there is
nothing wrong in advertising CIDR from two ASes as long as you can guarantee
each border router advertises CIDR only if it can reach it. Imagine the
following construction:
AS-A--\
          +(OSPF) --(CIDR)
AS-B--/

Each BGP speaker advertises CIDR if and only if it learned about it from
OSPF. It can be done, if you don't know how I'll forward you a working
example. Each border router generates a default router and injects it into
OSPF. From technical point of view I see no reasons why it should not work.
What you need is:
* An agreement between ISPs
* Change in procedure making such a union of ASes an officially blessed
solution so nobody would dare to hinder cooperation with filters.
* Optionally you may need a separate CIDR, since both ASes have to advertise
same prefix. You need it if each ISP wants to have private customers in
addition to shared ones.

The customer has "an independent connection to two ISPs" which is the quest
item. I see more commercial than technical problems with such a solution.
However my expertise is limited and somebody can point drawbacks I cannot
see. Feel free to burn me on a stake, that's the right way of treating a
blasphemy ;-)
Regards,
Jacek