Again, you're purely focusing on power. Removing concentration spells or this from the clerics choices during combat is balanced, but not interesting or fun. I don't want the cleric feeling like healing everyone every round is the choice they need to make rather than using their most interesting spells (which require concentration). I feel like we got away from that choice in this edition, where the cleric no longer feels pressure to heal others with their action rather than cast their most interesting spells, and you'd have this cleric basically go right back to that situation. And it doesn't appear, in any way, to enforce the sub-class concept involved either - that choice doesn't feel "twilight" to me. It's purely a power balancing solution. And I appreciate it does accomplish that goal but I don't think it accomplishes the goals focused on making this a fun class to play.
The way the mechanics work, the cleric can always heal and attack, or always attack and heal. This choice is just about which way the scale is tilted. It is never all or nothing. in either direction.