I'd dearly love the ability to have a few more spells to cast as a Ranger. Entangle is lovely, though it doesn't last long for me....gotta keep training with it...I'd like to see something else nature oriented. It just seems a waste of my spellcasting abilities that I can cast so many higher level spells and I only have one.
Maybe a HP drain spell that lets you transfer HP from your foe into yourself? A dual heal/attack spell of sorts.
Hmm, more animal stuff....perhaps a spell that draws on a Ranger's skills in animal empathy and/or wilderness lore and possibly even Knowledge (Nature) to actually SUMMON more animals into the area? This would only work in current hunting areas, and would only summon the critters that would normally be there anyhow....but I know people are always complaining about having nothing to hunt, or creatures not spawning fast enough.
Similarly, it might also be nifty to have a spell that would banish critters out of an area...I often get swarmed in certain places and would find it nice if I could convince some things to leave.
Both these spells would likely work best on animals, I can't imagine summoning or banishing a pirate very well....though who knows what would be possible with enough training.