He said he'd be pretty liberal about sources allowed since I am deliberately playing an underpowered character.
underpowered kobold? HA
kobolds can become VERY powerful (see pun pun)
since you allowed sources check this
Prestige Class: Swiftblade -- Haste Personified
and this
Web Enhancement: Races of the Dragon -- Kobolds: Of Traps and Perfection
if you want to stack with a pure melee class then i agree with StreamOfTheSky
I will say that in general, Tome of Battle makes everything better for a melee class, ideally if you actually play as one of those melee classes.
try crusader, it has a stance that gives +2 ac bonus vs foes bigger than you. at early levels you can achieve very high armor class.
BUT my suggestion, if you want to be the most capable melee character is to became a Sorcerer

by taking the dragonwrought kobold feat from races of the dragon you can be 120 years old (and die at about 220) with no penalties to str dex con and a +3 bonus at int wis cha.
+2 cha from the kobold paragon class
so start as sorcerer(1)
then kobold paragon(3)
and with the greater rite of passage you wont lose a sorcerer level
and then you have other options
one way to go is take 2 paladin levels and have incredibly high saves, continue as eldrich knight or abjurant champion and then swiftblade (this prc kicks ass

)
an other option continue as sorcerer and don't lose spell casting classes to take the swiftblade prc as early as possible so you'll gain the perperual options and innervated speed faster (the best class features ever

)
and an other option (my favorite) is the ultimate damage build,
desert kobold paragon(3)/sorcerer(1)/fighter(1)/unseen seer(2)/swiftblade(10)/spellsword(2)/sacred exorsist(1)
i don't remember the exact build very well and i don't have my notes right now
feats:
knowledge devotion
power attack
divine might
arcane strike
2wf
practiced spellcaster
traits: spellgifted (transmutation)
here is your damage output at level 20:
+5 from greater magic weapon
+1 - +5 from knowledge devotion
+8d6 sneak attack from hunter's eye (unseen seer(2) -> advanced learning (common trick))
+13 divine might (cha bonus with 5 points at level 20 and +6 item)
+7d4 arcane strike
+2d6 swift surge
+13 from slippers of battledancing (dmg2) that you MUST have
and even more with other tricks
don't waste feat slots to take imroved 2wf or greater 2wf, there is an item at magic item compedium that gives you the benefit of improved 2wf and you can also cast heroics
i'd take the domain access variation from complete champion to gain access in war domain and at the first round of combat (you'll always play first with init +19) use innervated speed and cast divine power to boost your ab. for the sneak attack you can cast greater invisibility or persistent blade