I re-read my original post and realised I was very scant on details, so I will update some information to skill trees, although I have made mention of certain features of skill trees in other threads.
Each skill/spell can be trained to 20 ranks, and only then, can you quest to attain mastery of that particular skill/spell. Mastery of any skill will gain a greater bonus than the usual rank addition. For example, stone skin spell will provide 1.5% damage absorption per rank, so at rank 20, the stone skin will provide 30% damage reduction. However, if the caster has mastery of stone skin, the protection increases to 50% less damage.
Each rank will cost 1 practice to gain - this is different from my original post.
There isnt just one main trunk in which players then choose different branches. There are actually many various "trunks" for each class, and players can choose as many trunks as they have practices available. For example, a weapons trunk will have slashing/piercing/blunt proficiencies which will lead to specialisations in specific weapons ie. sword, short sword, dagger, spear, etc. A unarmed combat trunk will lead to various martial arts branches. So a warrior may choose a particular branch which will lead them to specialise in swords, and choose another branch in the unarmed trunk which will give them monkey style martial arts. In this case, the warrior must choose slashing proficiency (accuracy bonus for all slashing type weapons) --> sword proficiency (accuracy bonus for swords only) --> sword specialisation (damage bonus for swords only), and also choose unarmed combat --> monkey stance (basic monkey fighting style) --> then various special monkey attacks (a few branches here for the warrior to choose from).
A player can choose any pathway they wish, as long as they have practiced the skill leading to it. A warrior cannot just choose sword specialisation without choosing the previous branches (in this case, slashing proficiency and sword proficiency).
Right now, all spells are categorised into 10 spheres, which I think is quite excessive, but thats besides the point. I am undecided whether to allow mages to just practice ranks in a particular sphere and they gain ALL the spells in those spheres, or the mages have to learn ranks in individual spells. I am leaning towards the latter option, as that will create a greater variety of mages. I will also compensate the latter option by providing more pracs for mages.
A wonderful example of this is, say mage casts a rank 15 wall of force, blocking people from going east. Another mage with rank 15 dispel magic will have 50/50 chance of dispelling that wall of force, whereas a mage with rank 5 dispel magic will have little chance of dispelling it. Same principle applies for someone with detect invisibility against a foe with invisibility spell. So it pays to have higher ranks for a particular spell when you are competing against other casters.
With this option, players will now get to choose whether to specialise in a defensive mage or combative mage, or be an all-rounder. As a previous example of this, an all-rounder may only have 10 ranks in stone skin, providing only 15% damage reduction, whereas a specialist defensive mage may have mastery of stone skin, providing them with a 50% damage reduction. Also, if a mage attains mastery in all spells in a particular sphere, they will become an elemental master and will gain special bonuses in that sphere!
With such a variety of characters for each class, players will need to find a good balance when they group together on hunts. It will be very interesting whether you need a bunch of specialists, or whether a group of all-rounders will prove more effective. Or perhaps, a mixture of both?
Just to be clear, we will retain our existing classes. Each class will have a selection of trunks in their skill tree list, some trunks will be exclusive, while there may be some trunks that are across several classes. There will also be general skill trunks available to all classes, for example, perception, athletics, crafting skills (armour and weapon making), etc.
I hope this clarifies some things.