I realise that making a two-handed or animal companion style might make the class overpowered due to stacking bonuses (Frenzied Berserker, Druid, etc), but how about other themes? The example below lays out something I would use in a heartbeat, even though it's value in combat is somewhat limited (it's more of an RP ability chain).
Survivalist Combat Style
The Survivalist spends a great deal of time seperated from civilisation. They must rely on their own fortitude and initiative to survive, and choose only the battles they can win. Unlike other Combat Styles the following abilities are retained when the Ranger wears Medium but not Heavy armor, although the Ranger gains no additional proficiencies.
2nd Level: The Ranger learns to rely on no one but themself when exploring the wilds, whether tracking down prey of healing their wounds. They gain Self Sufficient and/or Awareness as bonus feats.
6th Level: The Ranger learns to react to dangers almost before their senses can detect them, aiding them in both avoiding blows and detection. They gain Uncanny Dodge and/or Stealthy as bonus feats.
11th Level: The Ranger not only gains a sixth sense when it comes to attacking unseen foes, but their proficiency in healing wounds increases through experience. They gain Blind-Fight and/or Augmented Healing as bonus feats.
21st Level: The Ranger bolsters their mental fortitute just as much as their physical endurance. They gain both Iron Will and Indomitable Soul as bonus feats.
The Ranger can roll with a potentially lethal blow to take less damage from it than they otherwise would. They gain either Defensive Roll or Improved Evasion as a bonus feat.Oops, makes an easy step to Epic Dodge.
The Ranger becomes tougher overall (due to weaing slightly heavier armour, although they will need to spend a feat to aquire it), and some of the penalties are offset via the Stealthy feat. They lose fighting power over all, but they also become more well-rounded by being able to tackle different enemies (Blind-Fight, Uncanny Dodge). Better healing plays off the theme that Rangers are wise men of the woods who know poultices, etc. However they do NOT become more powerful when it comes to direct combat.
I don't think that's overpowered, but thoughts welcome.