Hey guys. Total newbie to HL here, and I'm blown away by the work y'all have done (especially the volunteers -- you're a great guy, Shadow).
But I had an idea regarding the Polymorph spells. I'm not a real programmer, so there may be some issues that make what I'm thinking of impossible/impractical, but here goes.
If you take Beast Shape, for example, there are a fairly limited number of spell effect options despite the countless variations of forms. Each of the levels of the spell (I through IV) enable different size categories of animals and magical beasts, and different special abilities that can be gained from the form. All told, there are 10 possible size categories (Diminuitive Animal, Tiny Animal, Small Animal, Medium Animal, Large Animal, Huge Animal, Tiny Magic Beast, Small Magic Beast, Medium Magic Beast, Large Magic Beast), each with a specific set of ability modifiers that are not (as I read the spell description) dependent on the specific animal/beast form chosen. A large wolf form grants the same +4 Str, -2 Dex and +4 Natural Armor bonus that a large horse form does. Similarly, there are a total of up to 25 special abilities that can be gained from the forms (including elemental resistances and vulnerabilities, which would technically involve 5 or 6 more each to include every element).
If you added a set of pull down menus for the size categories, and a radio button menu of the 25 possible abilities, then the user could simply select from those options and customize the available modifiers and abilities to whichever form was being taken at the time.
Again, I'm not really a programmer, so what I've just described may well involve decades of coding. But it seems like a much more managable project that the compiling of thousands of possible animal and magic beast forms that Mathias seemed to be describing in the opening post.
Of course, if this would be managable, a similar process could account for all the (much fewer) variables in the Elemental Body series, and the Plant Shape series, etc.
Hopefully this sparks some helpful thoughts.
Good luck, and thanks again for the really incredible work!