Rule #0
Of course, if you are not playing FR (or heck, even if you are) you can always ivoke your power as GM and declare that some half-outsider templates are "native outsiders."
Personally, I've always felt that you shoudl leave 1/2C and 1/2F characters as normal outsiders ((now there's an oxymoron)) and not allow them to be raised/res'd. If you make these templates into raiseable races, I'd icrease their ECL by 1, to a +4.
Also, remember that when an Outsider dies on the Prime, it isn't in fact "dead" it just gets returned to it's native plane. This is one of the reasons demons and celestials can afford to be so gung-ho when fighting on the Prime, other than an incoveniance, probably embarassament ("Hah-ha! Azifael got his butt kick by a paladin, agian!") they don't really suffer too much.
Another thought, if the player is making a 1/2C or 1/2F and whats to know what will happen to hi when he dies, I encourage the GM to shrug, grin and reply: "No one knows, although perhaps you'll find out in the next dungeon." (Then you should giggle.)
A PC shouldn't have knowledge about where they go when they die, except for what they hear at Sunday services and street-corner clerics. ("Have you accepted Pelor as your savior?") A Half-Celestial hero should be fairly one-of-a-kind. Preists and dogma may attempt to explain his afterlife, but they only way to really find out is to die.
As an aside, I also peg the Half-Elemental at ECL +3. Playtesting has shown it to be about equal to the Half-Fiend and Half-Celestial. Although each of them is stroner in a different class. (Fiends make great Sorcerors and Fighters. Celestials make great Clerics and Paladinds (duh) and Elementals make brutal druids.)