In addition to that. Yes for Cleric & Mages there should be an arcan focus (Grimoire) / spellcasting focus (e.g. Symbol on Shield):
https://www.dndbeyond.com/equipment/holy-symbol#:~:text=A%20cleric%20or%20paladin%20can,bear%20it%20on%20a%20shield.
You could also think about using battlestaffs not only for close combat, but also for elementary long-range combat like in GW2 or TESO. But maybe that's asking too much and we have cantrips for that.
Only bards have that right as of the last patch with their instruments. They use those for casting. We should just have casting slots that takes those items in same way. But the whole thing is half done same as weapons and range weapons combined with spellcasting focuses.. right now it's mix of everything with no heads or tail.
