Sorry, it was late I just wanted to leave a fast comment, and explain the rest later.
Links:
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Half-Celestial
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Saint
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So here I go:
"“
Half-celestial” is an
inherited template that can be added to any living, corporeal creature with an Intelligence score of 4 or higher and nonevil alignment (referred to hereafter as the base creature)."
Inherited meaning, the creature is born with the template, and can not be added to the creature later on in life.
"Size and Type: The creature’s type changes to outsider."
So the creature is an outsider from the get-go.
"
Saint" is an
acquired template that
can be added to any living creature of good alignment
that is not an outsider or an elemental (referred to hereafter as the "base creature").
Acquired means you add this template on to the creature later.
Summary: So since the Half-Celestial template is added applied at the start, the Saint template cannot be added, because the Half-Celestial is already an Outsider, and Saint cannot be added to the outsider type. That and you can only add the Saint template later cause you need to meet the requirements.
Now if your DM allows it, then its OK. In that cause just add up all the numbers slap the templates onto a base creature. Now you mention that its a gestalt thing, just use apply the LAs as classes levels, sort of, it would take up 6 class levels on one side (I'll explain this if needed).
PS: Don't take the half-celestial template, the saint on its own is better, what I mean is that the half-celestial is weak as a template for 4 LA, Meta-game wise that is. Ditch the Half-Celestial and go Saint all the way.
Just look at both templates character creation stats, some of them wont add up:
- Damage Reduction.
- The Saint gets some At-will powers that the HC only gets as a daily. (yes the HC gets better powers later on).
* HC: Resistance to acid 10, cold 10, and electricity 10.
* Saint: A saint is immune to acid, cold, electricity + the saints gets 10 fire resistance.
-The Saints immunities out shine the resistances.
Ok, I know its not all about numbers, fluff wise it makes sense to make a HC + Saint character.
That is all.