I'm thinking the character should be NG for alignment. I would plan on giving the Improved Familiar the Celestial Template via the Celestial Servant racial Feat. The character's role would likely be that of a party's primary healer but an in combat typical Arcanist.
My original idea was to specialize in [Light] spells but that seems like a very bad idea as the [Light] spells are mostly terrible. Flaring Spell Metamagic is still an option but I don't think I would use [Light] spells to do it with. More likely I would use [Fire] or [Lightning]. Consecrate Spell would also give the same feel and I could just fluff it to say that the spell is exploding in a burst of light.
Anyway, I think I would still like to keep the theme of angelic light with the Familiar so something that goes along that theme seems good. I had been thinking about a Positive Energy Elemental until I realized that it is 3rd party ... and no DM in his right mind would allow that thing as a Familiar. Another elemental isn't out of the question. I was hoping for something much like a Lantern Archon. Having a familiar that gives out small buffs and sits back and pew pews with tiny laser guns seems right up this character's alley.
I was also thinking of:
A Cassisian - But the idea of a flying helm is a bit weird for me. I would rather something either less substantial or something more humanoid or relatable. It is kinda hard to look a helm in the "face" and talk to it with any seriousness.
An Elemental - Probably Air. With the Celestial template I could just fluff it to be a small cloud of energy that seems to stay near my character. Not very helpful of a critter though.
Faerie Dragon - Of course, one of the most powerful Familiars. A DM would probably allow me to alter it's spell list.
Harbinger Archon - Mechanically this thing seems interesting as hell. Making it Celestial wouldn't do much, though. It sorta already is. It also can heal so thats cool. It also has pew pew Wrath scream? It does, however, have the same unfortunate issue as the Cassisian of being a flying astrolabe/orrery. That is weird.
Lyrakien - This thing is interesting and relatable too. It could help out a bit with the healing even. Even has a ranged blast. It doesn't cast like a sorcerer does so it can't accomplish the same shenanigans as a Faerie Dragon could.
Pseudodragon - Basically seems in all ways inferior to the Faerie Dragon except that it has a poison sting. I'd rather have the Faerie Dragon.
Silvanshee - These guys are dripping with flavor, just not sure it is the right flavor for this. No sorcerer spellcasting but it does have a few nice tricks. It also has lay on hands 1/day so it can help some with healing. They also seem like fairly defensible little guys so I wouldn't have to worry about it much.
Honestly the perfect thing would be a Lantern Archon but that isn't an available option. The little glowing ball of energy floating around the character is what I was looking for but the closest things to that don't make very effective familiars. I could fluff some of the existing ones differently and maybe a DM would go for it. Faerie Dragon is the most effective by far but I'm looking closely at Harbinger (refluffed), Lyrakien and Silvanshee too.
Opinions?
When I get something thrown together for a build I will post it but right now my mind is stuck on this part.
LazarX: Dispel Magic, Wands, Scrolls, Staves, Limited Wish, Planar Ally, Summoning spells, Heal skill, Craft (Alchemy) skill, Use Magic Device, and generally thinking outside the box say otherwise. I would love to see any constructive advice you might have.
darkwarriorkarg: Yeah. I was kinda thinking about that. The pew pew lasers and the unlimited aid might be enough for a DM to think it is over the top though. Personally, I think it pales in comparison to the Faerie Dragon's wand usage and telepathy. I could probably find DMs who agree with me. I would rather have a backup plan in case that fails though.
Ooo, I didn't realize that.