Mhhh…
Thinking about pet items made me miss mostly some offense on them for the player. Not much is needed and the gap of making hybrid styles playable with adding a pet to a build thats not totally useless could be made much easier to pull off.
There already are somewhat hybrid playstyle oriented items but not many builds are capable of utelizing the aspect of it in both ways; player dmg v/s pet buffs. As an example: Bysmiel trinkets have All dmg%/OA/DA on them with makes them nice to experiment with. Beastcaller has no all dmg% at all but some OA/DA. Adding some bleeddmg% for the player would maybe make some BleedBriar with player also stacking some bleed or stuff like that more achieveable. Devos are often boosting both sides in some way. So there is much already been set in stone
Considering some small changes the way pet aggro/taunt mechanics being used to find a healthy spot between player tankiness with aggro abuse and pet tank ability. (Like pet skill mods “that generate threat” taunt value ceiling)
Full force pet builds cant abuse something they dont need. So nothing to fear there.
Full dedicated melee/ranged/caster/etc builds dont care.
IF the attributes are balanced right (not that everyone runs with a pet sprinkled in lol) we get some new builds as a plus that get a bit more able to clear like cruci170/sr 65/75.
Demo + (Occu/Shaman/Necro)
would sound good as an idea that would profit from some pet item player bonus rebalance
Imagine some kind of DaShiv Pyro revival 
Or demo with skellies not being crap. Maybe even adding some nice mods for skellies being able to explode just like hellhounds (hint to improve hellhound explosive potential 
).
Somthing with Bysmiel Birbs, so Occu + Arcanist Trozan or + Shaman Lightnging/totems/etc could also profit that way.
Would really like to see buffs to pet items in that way if realizeable or of any interest.