So, I really like the idea of a wild halfling riding a pig. A badass little dude with a battle axe just sounds like a good time.
BUT the halflings -2 str is a real bummer, and I don't know enough to figure out if I'm making a mistake.
I was thinking about a dex build with a specialization in mounted combat. Using the outrider alternative racial trait and mounted fury archetype (info at the bottom).
Another option is the bloodrager hybrid class. Class skills there have a heavier emphasis on dex and it has a a 'bloodrider' archetype which is identical to mounted fury. Also, bloodlines which give nice bonuses.
OUTRIDER RACIAL TRAIT
Advanced Players Guide, PG. 21
Some halflings specialize in mounted combat. Halflings with this racial trait gain a +2 bonus on Handle Animal and Ride checks. This racial trait replaces the sure-footed racial trait.
MOUNTED FURY ARCHETYPE
Source Advanced Player's Guide pg. 79
Many barbarian tribes are masters of the horse, teaching their members how to ride from a young age. As a result, barbarians from such tribes are even more terrifying when mounted, using their steeds’ speed and strength to great advantage. A mounted fury has the following class features.
Fast Rider (Ex): The speed of any mount the barbarian rides is increased by 10 feet. This ability replaces fast movement.
Bestial Mount (Ex): At 5th level, the mounted fury gains the service of a feral mount. This ability functions as a druid’s animal companion, using the barbarian’s level –4 as her effective druid level. This companion must be one that she is capable of riding and is suitable as a mount. A Medium barbarian can select a camel or a horse. A Small barbarian can select a pony or a wolf, but can also select a boar or a dog if she is at least 8th level. Whenever a barbarian is raging while mounted on her bestial mount, the mount gains a +2 morale bonus to its Strength. This ability replaces uncanny dodge and improved uncanny dodge.
Rage Powers: The following rage powers complement the mounted fury archetype: ferocious mount, ferocious trample, greater ferocious mount, greater ferocious trample, and spirit steed.