Alter-Ego Build? (3.5/PF)

[F.H. Zebedee]

So, I was looking at Pathfinder's SRD, and the Synthesist variant on the Summoner caught my eye. I have a soft spot for mild-mannered characters who turn into invincible warriors, in such a way that they can't take credit for their deeds.

So far, so good. A Clark Kent/Peter Parker type, a nice enough guy who, when the chips are down, changes in an instant to somebody else, somebody dynamic and who those around them would never suspect to be the same guy.

Now, those of you reading are surely giving a nod to Rich's excellent Champion class, posted here in the Homebrew forums.

And here's where my idea goes totally off the rails: I want to make a character with two such alter-egos. One (the Synthesist Eidolon) would be fluffed as some natural (or unnatural) bond with a parasitic outsider, one that is tied to his soul and manifests in time of duress. Most likely Quadruped with Pounce, though that's about all I've decided.

And on the other hand, I'd like to use the Champion class. I'm thinking some sort of divine or angelic being, bound to him to keep the other side in check by providing him with a means to survive in a fight well enough so that the Beast doesn't take over.

The big idea for this character would be that he himself is fairly unremarkable, but eventually, between the influences of the two beings bound to him, becomes pretty formidable, and even becomes a mediator of sorts between the two sides.

So, three big questions:
-First of all, can Pathfinder be viably used with 3.5 in combination like this? My DM is very permissive, and has allowed a few homebrew things before (none of the players are munchkins, so it works okay), so I doubt he'd have issues with me using what is basically 3.75. I'm just wondering what I'd have to tweak about the Summoner (Synthesist) class before using it.

-Could this build work... decently? We don't have very high optimization in our group, tending towards concepts instead of power-builds. Heck, two of the four players are playing, respectively, an Arcane Archer and a Dwarven Defender in our current campaign. Would this build be able to work at level 2 (our standard starting level). What about 5-10ish? I don't think an alternate campaign to our current one would stray much higher, though knowing if it'd just totally suck at like level 15 would be good to know, too.

-Any advice for optimizing this Frankenstein? I know he won't be powerful by Char Op standards, but is there some way to make it so that he could keep pace with a Beer and Peanuts style group?

[Prime32]

So, three big questions:
-First of all, can Pathfinder be viably used with 3.5 in combination like this? My DM is very permissive, and has allowed a few homebrew things before (none of the players are munchkins, so it works okay), so I doubt he'd have issues with me using what is basically 3.75. I'm just wondering what I'd have to tweak about the Summoner (Synthesist) class before using it.Just the skills. Add Concentration, remove Fly, split Linguistics into Decipher Script/Forgery/Speak Language.

Was this going to be a gestalt build?

[F.H. Zebedee]

Ah, thank you very much. That right there really smooths things out a lot. :)

We don't have a specific alternate campaign going yet, but I was considering this for a backup character for when we do. And indeed, Gestalt seems to be where this build could actually be functional. I'll have to bring that up as a possibility for later; I'm sure the other players would love it.

Thanks for the advice!

[Telonius]

Would it be possible to just use your Champion build, with afflicted Lycanthropy? That's certainly what it sounds like. Hero Form would give it a better Will save to resist the Lycanthropy.

EDIT: You could simply re-fluff the transformation to be to a devilish or demonic form. The Resistance 5/silver already works if the outsider is a Devil.

[Venusaur]

The funniest alter ego build is a halfling that takes the stoneblessed prestige class to qualify for the goliath barbarian ACF mountain rage. Then you take the War Hulk prc from miniatures handbook. This gives strength instead of BAB. So, when your halfling gets mad, he gets large and a ton of strength.

[F.H. Zebedee]

Ooh, Lycanthropy! I didn't even think of refluffing that, but that'd be perfect, too. I'll have to have both ideas set aside; I've never had any other idea that really jived with a gestalt campaign, but if we do a standard (or my guy in our current standard campaign bites it), the Lycanthropy workaround is pretty much perfect.

And there's a lot of feat support for growing to control/utilize one's lycanthropy, so that actually lets him grown into the role where he starts using it, instead of it using him.

Between those two options, I'm genuinely excited for this idea. Seems whichever way I go, it can actually work out pretty well. :)

Also, Venusaur, I'm totally dubbing that build the Hulkling. ;)

[Rhaegar14]

I'll also mention the Master Chymist Alchemist-oriented Prestige Class for Pathfinder. It can be found on the SRD, and it basically makes you Dr. Jekyll with a Mr. Hyde alter ego.