I like your ideas, besides Capella giving knockdown/back immunity, that for me looks too much party-wise , and also Binatio might end up being overpower. But on a single-target aspect, might be OK anyway.
The sad thing is that Chaplain falls apart exactly where it was supposed to shine, auto attacking. I said it before: melee auto attack is terrible. QS was a thing because it was ranged and RS gave high mobility too, while attacking at the same time. Besides the auto attack aspect, Chaplain doesn’t provide anything else for other builds, it’s a complicated dependency relationship.
Devs can make it work, but at the cost of making melee auto attack too powerful for a single target aspect, which would be fine for me specially if you consider that Monk and Chaplain have no range to a small one. With Sadhu you gain more skills, but not sure if we gonna see again the glorious days of Sadhu Spirit Auto Attack anymore.
EDIT: also… and what about the thing of the new Scout tree was to be the branch for auto attacks? Corsair is there, with a lame DWA, only viable AA class is SR, as always. This would give another PoV for these Cleric classes, if they ever consider removing this aspect from Chaplain entirely, and making Monk viable outside of it too.