I've been searching around trying to find a proper answer, but I haven't found one yet. For the purposes of the following examples, I am using a spear.
The description for a Shrinking weapon (from the Melee Tactics Toolbox) says that it shrinks to the size of a standard dagger and its damage is reduced to 1d4. Beyond this there is nothing to clarify, as others have brought up in previous threads. There's also no FAQ I can find regarding this book or magic weapon ability.
I take this to mean that a shrinking spear in dagger form is still otherwise considered a spear. Is this the case, such that having Weapon Training (Spears) or Weapon Focus (Spear) would still function and grant their bonuses in dagger form? (This is the primary question for this topic.)
It would also be a light weapon (as normal for a dagger-sized weapon), but would otherwise remain a spear and have a 20 ft throwing range, x3 critical multiplier, and the brace ability. I could absolutely see a case for abilities like brace and reach not applying in dagger form, since there are no other light weapons (in any proficiency category) with either.
Given the reduction in size, the weapon would no longer gain the +50% bonus damage from Strength or Power Attack, but assumedly it's still a weapon of its original size category (Small, Medium, etc), simply in a different weapon size (Light vs Two-Handed). If this is the case, and the answer to the primary question is "yes", that would mean that the warpriest damage scale should still function. (Also relevant for fighters with the Focused Weapon advanced training option.)
Is it still a two handed weapon? :-)
While still in the shape of a spear, I think the feats would apply, but you now run into using weapons not sized appropriately for you. Either that, or the improvised weapon penalty.
For throwing range, is that affected by size? I.e. a spear for a small sized character is a different size than a spear for a medium character. Do the spears have the same distance?
Crit should be the same, as that I think is more based on the form of the weapon.
Brace would go away, since you need to brace against something, and a dagger sized spear it too small to do that.
.cevah