...I would like it to more meaningfully change the rangers kit to provide some mechanical uniqueness to each option. The minor buffs in different skill proficiency don't actually do a ton to add to character flavor or function where as I think changing how certain abilities function depending on favored enemy or what spells can be accessed during character progression would add more depth to each favored enemy option and therefore to the ranger class as a whole.
This I largely agree with. I think the Bounty Hunter, for example, is a good indication of how these features could be implemented well. I would like to remove the skill proficiency bonus, because it makes Rangers a 4 skill class when they are balanced around being a 3 skill class, but the idea that you get a special benefit when using the Ensnaring Strike spell is a cool way to give it flavor and impact.
Let's write some potential features that adresses the actual design problems Rangers have (too few spells, mostly useless flavor features) at lower levels, but that doesn't go outside the normal abilities a Ranger would have:
Bounty Hunter: You add the Ensnaring Strike spell to your spellbook. It does not count towards the number of Ranger spells you know and you cannot exchange it for another spell. You can cast Ensnaring Strike once per long rest without expending a spellslot, and normally with spellslots after that. Enemies have disadvantage on their saving throw when they are hit by an Ensnaring Strike cast by you.
Beast Tamer: You add the Speak With Animals spell to your spellbook. It does not count towards the number of Ranger spells you know and you cannot exchange it for another spell. You can cast it as a ritual (free, out of combat). You have advantage on dialogue checks when interacting with animals.
Monster Slayer (default in character creation): You add the Hunter's Mark spell to your spellbook. It does not count towards the number of Ranger spells you know and you cannot exchange it for another spell. You can cast it once per long rest without expending a spellslot, and normally with spellslots after than. You have advantage on saving throws to maintain concentration on Hunter's Mark.
