On Furious Gladiator, there are lots of alternate rages already. Why not just make a whole new type of rage instead of trying to tone down normal rage? Or base it off another type of rage.
Example: Base it off of Whirling Frenzy, replace the extra attack with the form switching. Remove the Reflex bonus since you removed the Will bonus from normal rage.
New Comparison:
Level 1 Rage: +4 Str, +4 Con, +2 Will, -2 AC
Level 1 Furious Gladiator: +4 Str, +2 AC, enter form when raging
Level 11 Rage: +6 Str, +6 Con, +3 Will, -2 AC
Level 11 Furious Gladiator: +6 Str, +3 AC, enter form when raging
Level 17 Rage: +6 Str, +6 Con, +3 Will, -2 AC, no fatigue at end of rage
Level 17 Furious Gladiator: +6 Str, +3 AC, enter form when raging, make bladecraft checks to prolong rage
Level 20 Rage: +8 Str, +8 Con, +4 Will, -2 AC, no fatigue at end of rage
Level 20 Furious Gladiator: +8 Str, +4 AC, enter form when raging, make bladecraft checks to prolong rage
You could say that techniques and rage aren't compatible, but in that case be prepared to have a barbarian who knows techniques to be a rarity unless you make it a feat tax or wrap it into a prestige class or make it a higher level rage ability, etc.