This is an offshoot of the "external training for internal arts" thread, on which the consensus seemed to be that external training was innapropriate for the internal arts.
Now, let's say I want to throw someone. The way I see it, good throws with good technique are based on leverage - the larger the range of motion the throw goes through, the less effort I have to expend to execute it. Same with a simple lever - I can lift a very heavy weight with little effort if I expend that effort over a larger distance.
Now to me, this is the basis of good throwing. There are other factors, like putting your body weight into the throw, staying relaxed so you can adjust the direction of the force you're issuing on the fly, catching the guy off guard, getting his momentum going in a way that aids your throw, etc... - to an extent, these are all matters of timing and experience. The heart of the throw is the lever.
Now for "internal" strength. The way I see it, a good internal stylist can execute a throw with comparatively little muscular strength because he or she uses this principle. So, a small person can throw a big one, and this is "internal" strength - not so much strength as technique that, in effect, "multiplies" the effect of whatever strength is used. Internal skill is a multiplier.
However, what I'm hearing on here is that internal stylists use a different kind of power generation altogether - that they use their tendons, and their bodyweight exclusively to generate whatever power they need? In this case, internal skill is a method of generating power, independent of what we usually call "external" strength - so developing external strength will not aid your ability to throw someone using internal methods.
The way I see it, any throw will meet resistance - both from your opponent's muscles and from his inertia. If you divide that resistance over a larger range of motion, it will decrease and you'll need less effort to get the throw. However, even in internal arts, you're still using your muscles to apply whatever force is needed.