Update: Brawler archetype from UC gives an awesome +1 attack / +3 damage with all close weapons at level 3, and +1 bull rush and a few other maneuvers at 2. It's perfect for this build! Sample level 9 optimized build with 25 point buy:
[sblock]Oread Guide Ranger 6 / Brawler Fighter 3
Str 18, Dex 16, Con 14, Int 12, Wis 14, Cha 5 (25 point buy)
Str 20 (22), Dex 16 (18), Con 14, Int 12, Wis 14, Cha 5 (final)
HP: (9d10 +18 +6 favored class)
AC: 28 (10 +8 armor +3 dex +4 shield +1 deflect +1 natural +1 insight)
Saves: Fortitude +11, Reflex +11, Will +6
BAB +9/+4; CMB +15 (+20 bull rush), CMD 31 (36 bull rush)
Full Attack
Shield +21/+16 (2d6 +13, 20/x2, P) and Shield +21/+16 (2d6 +10, 20/x2, P)
Special: Bull rush on each hit, using attack roll +5 for the maneuver check
Feats:
1 Imp Shield Bash
2 Shield Slam
3 TWF
5 Weapon Focus (Heavy Shield)
6 Shield Master
7 Improved TWF
7 Power Attack [Fighter]
8 Improved Bull Rush
9 Greater Bull Rush
Gear (46000 gp):
+2 Bashing spiked heavy shield
+2 Bashing spiked heavy shield
+2 Breastplate or Kikko Armor
Gloves of Dueling
Strength +2
Dexterity +2
Ring of Protect +1
Natural Armor +1
Dusty Rose Iuon Stone
Cloak of Resistance +1[/sblock]
Ideal final armor would be mithral full plate, O-Yoroi, or Tatami-do, just too expensive at level 9 to be practical, IMO. Note that it can use Guide Ranger's Focus ability 2/day for +4 attack and damage, also.
I rather like this concept, shame there's no decent PF feat to apply shield bonus to touch AC or lend an ally your shield's AC bonus yet.
EDIT: Forgot Shield Master completely negates the TWF penalties.