I mean, yeah, you’d definitely be able to play support with that build. The problem with comparing Clerics in ToS to Clerics in other games is…well, those are other games but you already said you want to do it so okay.
Here’s what I’m trying to figure out. You said you don’t want to do damage but now you’re saying you don’t just want to heal/buff. Cleric and Priest are all about doing exactly that. Cleric has Safety Zone which is great for PvE but PvP is just too mobile and most classes have CC that will either knock you out of the zone or prevent you from doing anything (Sleep, Stun, etc.) while you’re standing in it. That’s why Diev3 is so popular. Statue of Ausrine gives you invulnerability and mobility at the same time. Druid2 has Sterea Trofh which is similar to Safety Zone but with a much larger AoE.
But since you’re dead set against Diev and Inquisitor, that set up is pretty much optimal.