Its a pretty simple suggestion in my eyes. Make it so that Training Skills don't have to be slotted when invested.
What's the Reasoning for this?
With the way that the Skill system is set up in the Witcher 3, You have to both; invest points, and slot skills in order to receive the bonuses from skills. This works fine, and I even enjoy the system. Pairing skills also has the added benefit of enhancing Mutagens you slot for increased bonuses. The fly in this ointment is that the Mutagen system makes investing and slotting in the Training the Tree a pointless endeavor -- despite the many bonuses with in it.
Furthermore, the argument could be made that the Training Bonuses are bonuses that Geralt should have native. Hence the name of the tree these bonuses are in.
In short, the Training Tree is either worthless, or redundant when taken in mind with the Slot Budget in the system, and the Mutagen System.
How should this be fixed?
I have a few paths that could be taken.
1. Remove the ability to slot skills from the Training Tree and make them function as if they are slotted. This makes for a worthwhile investment in these skills, and makes them not interfere with the 3 major trees.
2. Remove the Training Skill Tree altogether and make these bonuses native. Geralt is a seasoned Witcher, therefore at this point in the series, his training should be second nature.
3. Make Training Skills function as 'Wild Cards'. Training Skills will act like skills of a certain tree as far as Mutagens are concerned as long as it's paired with 2 other skills of that tree. 2 Combat Skills and 1 Training Skill will function as 3 Combat Skills for the Mutagen Slot.
What will this change?
This will make points invested in the Training Tree worthwhile, and not take away from Mutagens or our Slot Budget. This will also, depending on he path taken above; Make the Training Tree a worthwhie investment of our few skill points, lower the Difficulty of the game, or Create more Diversity in Builds without having to take a hit for not meeting all of the bonuses on your Mutagens.
If you agree with this, post in this thread with your approval, the more positive posts, the more likely it is to pass from the Community Managers, to Developers.