Personally, i find it very disappointing and mildly interesting how a fair number of people think about these kinds of measures as "punishments" or "penalties". Which they are not.
These are balances.
But, to some number of people, that is like saying "the glass is half empty". They just see it in negative light, as a measure that is taking away something from them.
Not that i can change anyone's mind about it but, the main point of such measures is making the whole game better - not just giving you more and more and more powers, spells, abilities, loot or whatever.
You cant just keep upgrading specialists and then hybrids and then specialists in turns indefinitely.
Ah, dont mind me folks, thats just a part of the bigger theory and philosophy of design of RPGs.
Lets get back to immediate matters.
There are few things in the op that are not correctly presented, so i just wanted to mention those.
- Talents that are only accessible at rank 4/5 of a particular school of magic.
While I like this concept in theory, I feel that it fails in practice since the talent will fall into one of two categories. (1) The talent is not powerful enough to solve the problem, and the all-round wizard build is still more powerful. (2) The talent is powerful enough to make specializing worth it, but now every specialist is forced to get a particular talent.
This is not really true because Talents are not meant to "solve" anything.
Talents are additional improvements, not solutions, that are given as rewards to reaching specific levels with specific builds.
There is nothing wrong with them. There only should be more of these small additional boosts to various skills.
Magic schools dont have any talents right now, or almost none.
And a Talent would be a great way to introduce either specific AP reductions for specific spells or level of spells. Or Cooldown reductions for a specific type of magic or whatever.
All these can be minimal - but would still feel great for the players and the sense of character progression.
- In general: any sort of boost in damage / other bonuses (AP cost reduction, etc.) for investing towards a particular school.
On top of suffering from most of the problems mentioned above, these sort of fixes create a balance nightmare. A skill must be worth using when someone only has 1 point in the school of magic, but must also not be overpowered for someone who has specialized in the school. This must somehow be accomplished while making the bonuses large enough to reward specialization.
Only if you see it and present it in such an overblown manner, to boost your position that way. It is not a "balance
Nightmare" - it is just ordinary balancing.
A "skill" - meaning all skills, does not need to be "worth using" to "someone with 1 point" - because there is no need for that to be applied to all skills, equally, to all builds - because of level, Intelligence or other attribute requirements, which dont allow all skills to be usable.
Or allow it but with lesser efficiency. As they do now.
Different builds will find different skills more or less worthy. And thats fine. A single skill does not need to be equally worthy to every build.
- Certain spells require a particular level in the type of magic along with the level + intelligence requirement.
Once again, this limits build diversity, puts us into a more class-like system, and makes players feel like they have to specialize much more than they actually need to. To get a school to rank 5 and access to those abilities, you need 15 points, which severely limits how many you have left afterwards.
It does not "limit build diversity" - it just makes players actually invest something to achieve it instead of allowing it for everyone for nothing. Which would be unbalanced and would practically force all players to do that, make such builds.
But, i do agree that your idea of allowing all or most of the spells to be used, with AP costs depending on level of the specific magic skill is a good idea.
Yours is basically a soft limit, instead of a hard one.
Or, for those that see glass as half empty,... - its a soft border, that you will be able to cross and get whatever is behind it.
