I'm not technically opposed to hundreds of planets (which is latest tack Stern, etc. are taking, having recognized that nine is _never_ again going to fly). Just opposed to nine, which makes the least technical sense of any alternative.
You have an incorrect understanding of Stern's views on this. Here is really good read on planetary classification (Stern & Levison 2002):
Certainly as of 2002 Stern was proposing there are many more than 9 planets. In the paper linked to above he defined the following types of objects:
Planetary body --> Condensing what was written in the paper: a body that is massive enough to be shaped by gravity into a spheroidal shape but not so massive that it has ever has core nuclear fusion (not a brown dwarf or star).
Stern & Levison then define the following terms:
Planet, planetary scale satellite, unbound planet
Planet is defined as follows in the paper: "A planet is any planetary body on a bound orbit around a single or multiple star system; by our definition, the classical 9 planets, as well as a few of the largest asteroids, and very large KBO's, qualify."
So in 2002 Stern & Levison were proposing many more than 9 planets. I'm not sure where you are getting the idea that Stern wants, or has ever wanted just 9 planets. But that is not the case.
Another important thing this paper gets into which the IAU really botched is an understanding of sub-types. Stern & Levison discuss dynamical classification and make the distinction that the IAU later defined as planets and dwarf planets. A dynamical dominance definition did not first come with the IAU. Stern & Levison proposed it in 2002. From section 6 of their paper:
Stern&Levison 2002: Our goal for a dynamical classification scheme is thus to determine whether any given body is dynamically important to the system in which it is found. Hence, we define and uberplanet as a planetary body in orbit about a star that is dynamically important enough to have cleared its neighboring planetesimals in a Hubble time. And we define an unterplanet as one taht has not been able to do so. It is important to note that, unlike the physical criteria for planethood, these purely dynamical criteria cannot be an intrinsic aspect of a body, but is necessarily dependent on the environment and dynamical context in which a body finds itself."
What Stern&Levison proposed in 2002 is basically what the IAU did. Uberplanets are IAU planets and unterplanets are IAU dwarf planets. But there is an important distinction which is the reason for the controversy. The IAU decreed that dwarf planets are not a type of planet.
Stern & Levison's paper illustrated the taxonomic idea of a broad category and sub-types that is lacking in the IAU system.
Now you have said that you do not object to hundreds of planet, but just to nine. Since I cleared up above that Stern is not proposing 9 - and never did, I'd like to ask what objections you might have to what I have proposed. Here they are:
Brown dwarf: Sub-stellar mass body (<~60 Jupiter masses) formed by star-like gas collapse mechanisms that did not acquire sufficient mass to sustain core hydrogen fusion.
Planet: Sub-stellar mass body formed in a proto-planetary disk with sufficient mass to self-gravitate into a spheroidal shape.
Dynamical Classes of Planets:
Principal planet: planet orbiting a star or brown dwarf that dynamically dominates its orbit (IAU planets)
Belt planet: Planet orbiting a star or brown dwarf that does not dynamically dominate its orbit and therefore shares its orbit with numerous bodies that have a combined mass greater than the mass of the belt planet.
Satellite planet: planet with orbiting a larger planet.
Satellite/moon: sub-stellar mass body formed in a proto-planetary disk in orbit around a planet or dwarf planet with insufficient mass to self-gravitate into a spherical shape
Rogue planet: planet without an orbit around a star. Since this type of body must have formed in a proto-planetary disk it has been ejected from its orbit.
A useful aspect of the above definitions is that they are compatible with a body changing dynamical circumstances.
~1. A belt planet is captured into an orbit around a principal planet and therefore its dynamical class shifts from belt planet to satellite planet. An example of this is Neptune's large Satellite Triton, which is a very Pluto-like body Neptune captured from the Kuiper belt. At one time in its history it was a belt planet. Now it is a satellite planet.
~2. A principal planet, belt planet, or satellite planet is ejected from its orbit and no longer orbits a star. It has now become a rogue planet.
~3. Migration of a principal planet's orbit shifts it outward into the Kuiper belt where it no longer is more massive than the combined mass of the other bodies in its orbital zone. The dynamical class has shifted from principal planet to belt planet.
I did not address the concept of "double-planet" or "double-dwarf planet" but neither has the IAU. However, I did address that concept and much of the above in this paper:
Take some time to analyze all this and let me know if you can think of any arguments why the IAU definitions are more useful than what I have described.