Would it really matter? Your stamina gets drained in such large chunks chance are you aren't even going to be able to use all those spells and abilities. The only thing I would recommend and could imagine them doing is making the Focus ability a separate thing entirely, and only allow us one Focus Ability. They're so important they're needed, so its like we have 7 instead of 8 really.
I was worried about 8 spells before I played the game, but when I did I realized the game was balanced around it, and adding in 20 more spells would just be redundant
you do have a point I saw while writing my original comment, yet I dont agree completely.
lets say you played a mage and had cold and fire spells. you use fire most of the time, but then you encounter a rage demon (or other creatures which are resistant or immune to fire) and so you need to use cold.
besides - wouldnt it be better and more easily accessible for you to have your combat spells mapped to 1-4?
apart from that - I play a dagger rogue, and those have a few skills which are kinda hard to part with. :-) since they have their use - e.g. twin fangs is fine, but becomes obsolete for stealth strikes when you get Shadow Strike, yet is still useful in regular combat (while your stealth generators are recovering). but with 8 ability slots you have to choose between them. not to mention that you get more and more skills with specialization classes...
and the recovery isnt that terrible on rogues, imho. but its not really the point in this topic, even though it may seem like it is. the reason is simply because your current situation may call for a different skill, not for you using 30 skills at once, thus it would come in handy to have slots where you can map that skill, wouldnt it?
I hope I made sence there, because, frankly, I had to re-write that last sentence a couple times. :-D