More slots is a very weak incentive to invest a lot of points into skill levels. Or not an incentive at all.
If i have diversified (which i always do since i like to play hybrid builds) - i gain many many different spells from each magic branch - element. Or many different skills from other ... martial skills. All these are the ones i like best, the most powerful and useful of all available.
But if i spend that many points (1 - 2 - 3 ... etc) into a single skill... all i get is 7 slots? I can just change any spell or skill in those slots as i please, more or less. Buying skill books is easy.
Which makes needing more slots quite unnecessary.
Especially because all skills and spells are not equally useful or good. There are several ones which i will never use.
And the choices are quite constrained all the same.
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Some posters would want a return to the previous system - which is not possible.
I wouldn't - but i would like something to be added to the higher skill levels to make them more valuable, something that would create a better incentives for spending so much points into them - rather then almost none they have now.
I think that if these incentives are relatively smaller features and effects, it might be something that could be added in time for the full release.