As for specialized fighting shields I always envisioned spiked shields and giant circular saw blade looking shields for some interesting combos. Or something that acted like a tower shield, but would split in two halves to let you fight with one on each arm. In no way was it common enough like you said to be something that would work on more than one character. (In my case a Psychic warrior lizard folk using full plate and with the oversized two weapon fighting for two heavy spiked shields)
I may eventually work up something of a feat for it (maybe something like shield fighting basics or some such) but overall, I think that your oversized gauntlet idea sounds way cooler. *has flashbacks to those crazy gauntlet things from Conan the Barbarian in the pit fight scene*
The shield feat chain is locked down now and gives about a 2:1 balance of defensive and offensive benefits. The standard shield is giving you a +2 bonus to defense, a nice compliment to the penaties armor can impose, but also making the unarmed Sword & Sandals warriors pretty happy. Drop a shield master ina doorway and it could be a long, long time before anyone gets past him. I expect to hear some wide-eyed squee when the first generation of Fantasy Craft
soldier characters start going over their options, because a number of the other chains synergize beautifuly with shield use.