Is it possible to add attribute modifiers from this mod to weapons/armor/etc just like in the vanilla?

no

do you plan to implementing stats for items in some way?

Hmmmm I'm not sure, weapon stats are kind of wasteful, the attributes are saved to the player forever where an armor piece is disposable.

or what do you think?

well dont know what of kind of techical restrictions there can be, but my point is that: when player wear some pice of gear or set of them he gains boost for certain stats or even +1 point for skill. Whenever equipment is taken off these bonuses no longer should applies. I suggest that because right now entire progress of the mod is centered around earning XP which is already essential things for enchants, If there will be and option to customize stats for any equipment included modded ones this will be insanely good for modpacks.