Roundtable's page

Jason, SRD:

Splash Weapon Mastery
Benefit: When throwing a splash weapon, you act as if you had the Far Shot feat. When you hit with a splash weapon, select one additional square adjacent to the splash area; creatures in this area also take splash damage. When you miss with a splash weapon, you may adjust the miss direction on the grid by +1 or –1. This feat counts as Far Shot for the purpose of qualifying for other feats, but only in regard to splash weapons.

Start with Eagle, Giant (who is large)
And then Jason, the guy who made the Shaman archetypes, even states that he recommends allowing one to use the young (For a huge Roc) or the giant (on giant eagle for a huge eagle)
He does say polymorph effects don't allow you to become templated creatures, but doesn't site where (at least in the thread I'm linking)
http://paizo.com/paizo/messageboards/paizoPublishing/pathfinder/pathfinderR PG/paizo/aPGDruidShamanWildshapingModifiersWhatDoTheyMean&page=1&so urce=search#5

Basically you use the damage die types for the adjusted size and the beast shape stat mods (not the actual template.) I do believe I've also seen a thread or two where people seem to have already used this variation, so it doesn't seem that uncommon.

Edit: Oh, it sneaks in on the specific individuals paragraph:

"Unless otherwise noted, polymorph spells cannot be used to change into specific individuals. Although many of the fine details can be controlled, your appearance is always that of a generic member of that creature's type. Polymorph spells cannot be used to assume the form of a creature with a template or an advanced version of a creature."

I know I'm running a completely different system, but I've decided to introduce the idea of evolving items. In particular I'm going to reward the Swordmage for maintaining his bond by gradually increasing it's power for him. I just gave it it's first +1 (overdue at level 4 I know, but the first part of the adventure was purposely poor. ) after a tough close quarters brawl with Kruthik in which he nearly went down twice.

It let's me give the next best item without the whole "Good, I picked up the +2, now to pawn the +1" thing coming up for every upgrade.
My Campaign does involve going near sites of power, so that add a little more to the idea. I'm also essentially upgrading everyone with a free teamwork feat for completing the first arc and saving the mystic pillar.