Gluten-Free Baker's Percent

Hello everyone.

I'm baking gluten-free bread since August and I have achieved good results with trial and error. But now I have entered into the development of new products and I'm thinking of Baker's Percent (BP) to create the recipes.
Since gluten-free use additional ingredients to achieve the "gluten" properties like eggs, gums, milk powder, baking powder, etc. The problem is when I tried to get the % hydration, why?:
1) The dry ingredients that recreate the gluten (gums, cellulose, baking powder) should be part of the flour?
2) As the GF recipes use eggs, should I count the 74% of water on an egg as water on the BP?

Example:
- 400 g. GF Mix [30%tapioca starch, 30% cornstarch, 30% rice flour] (GFM)
- 15 g. Skimmed Milk Powder (SMP)
- 9 g. Xantham Gum (XG)
- 4 g. Baking Powder (PB)
- 8 g. Salt (S)
- 2 u. Eggs (E)
- 8 g. Instant Yeast (IY)
- 16 g. White sugar (WS)
- 250 g. Water (W)

So to take a hydration percent, which of these alternatives is correct?:
1)  W / GFM
2)  W / GFM+SMP+XG+PB
3)  W+(E*74%) / GFM
4)  W+(E*74%) / GFM+SMP+XG+PB

Cheers,