This would require me to choose one or the other..
Choose one or another what...?
The 16 basic talents only affect the x2 training skill like it is now, you can pick whichever one you want.
As for the talent title bonus you can use the hidden talent of magic (Mage) + bless (Priest) = Sage.
Is a title system that reward you for specializing in certain area, very much like wearing Magnum Shot Master when you mastered Rank 1 Magnum Shot.
It is no different than when people say "I play Magic Warrior Style (magic + melee)" and rewarding you certain stats for being that "build" (similar to when you rank archer skills you get dex).
More or less, with translation preferences... and Striker is not "all", Striker is all of Melee.
Aside from that, hidden talent title takes the average of the combined skills. If you are say Lv. 15 Lancer (Lance) and Lv. 1 Priest (Bless), you will get the Lv. 15 lancer bonus with Lv. 1 priest, but when you use the hidden title it will be Level 8 Holy Lancer (15 + 1)/2 = 8. And yes that means you can be same level talent but have different bonus from hidden talents: 15+1 vs 8+8 vs 1+15. If a title takes 3 basic talent it will be divided by 3 instead etc.
There is an everything talent called Extraordinaire but... most sources mark them as ? because... like Striker I don't believe it's implemented yet. And whether it will be a testing only thing is also uncertain. Because mainly these are just from text files.