i know i'll probably get destroyed for saying this, but what i would love to see is a skill tree system for each class (maybe 3 branches each?) but once you pick one tree, there is no going back. for example: you can be a wizard, however there are 3 classes of wizards: white, red and black. each class has its own branch of abilities and spells and different advantages/disadvantages. and even within those branches, you get a certain allotment of points and are able to put them into what you want (dps, buffs, heals, mez, familiars, etc...) so even within each branch you can funnel all your points into dps for instance, but that makes you weaker as a buffer or a healer. or perhaps you want to be a jack of all trades, but you're not super powerful in any one particular area. that way, you could literally have dozens of wizards (one class), but with dozens of different play styles. you could do this with every class in the game and give people a hundred different builds to work on, each one being unique in some way, instead of everyone getting the exact same spells/skills/abilities as every other similar class.I like it. Free-form character development has always been a favorite of mine, and this pretty much matches my ideal of a perfect system to a T.
I had drawn out a similar but slightly more rigid system more akin to one of the Final Fantasy job systems. Essentially, you have abilities divided up into sets of Active abilities (your "class" abilities - for this example, let's say Necromancy) and a pool of Support abilities (passive character developments, mostly - Run Speed, for instance). Active abilities are determined based on your current job/title, possibly with the addition of less-effective dual-classing to offer a smaller, weaker set of abilities from a different class (which also allows you to create something along the lines of the EQ hybrid classes dynamically - a Warrior class with a Necromancy subset would essentially be an EQ Classic Shadowknight). The Support abilities are equipped to the character from a pool of learned abilities, based on a point value and maximum capacity (Run Speed is 2 points, your character currently has a 10 point allotment).
and yes, i know WoW has trees, but you can also just spend a few gold and get all your points back and redo them any way you want. think it would be much more intriguing if the decisions you made with your skill points were final.