I vaugly recall it being mentioned that Class/Skill specific Lightstones/Artifacts were a possibility in the future. I hope this is still on the To-Do List. I'd really like to see some more class skill build options outside of Rabams. I doubt we'll ever see a Paragon/Optional Passive Tree, but having Lightstones and Artifacts that can maybe gain Imprints(Similar to Black Desert Mobile) to further diversify how classes can be played would be an excellent addition imho.

Imprints on Mobile would also be a potential option to expand on class roles/archtypes. Conditional options, like hitting a target with a Stun(PVP/PVE) will add 50HP per target hit etc. Giving players reasons to test out and revisit other classes to expirement would only help attract players that love spending hundreds of hours trying to experiement and find interesting interactions and combinations to make classes feel like their own. Thoughts?

its funny u mentioned that coz there is already a class spec in the game that basicallly has mandatory lightstone set to even use its kit normaly.

Several class specs, actually. 

we literally have unusable skill without 4x mind lightstone set.

Which ones? What skill is unusable without the extra resources from mind?