Should Skills be like this?

Woodcutting is a prime example of this. There's 5 ways to effectively train:

Extra Fast, without any money (ivy)
Fast, with little money (willows)
Medium, with some money (maples)
Medium-Slow, with a sum of cash (yews)
Slow, with a lot of money (magic)


Well... should all resource skills work like this?

Some skills have parts of this. Mining has granite, fishing has sharks, but they'd need some updates.

Depends. Runecraft would definitely benefit from all of them, but the Magic-market wouldn't profit from the Extra Fast (which is what they want).

I don't mean every skill... updated

Resource skills are what I mean, would they need it?

Of course I agree, it is what makes a skill balanced and makes people want to train it. However, I think fishing is already divided in this way...

Agility isn't really a resource skill

Could you split this for Fishing? Would it be like this?

Trout/Salmon
Lobster
Monkfish
Sharks

nope...

Rockfish must be slow... they're so high leveled.