Honestly, a less punishing Cleric Stance sounds pretty nice and I don't really see anything outright terrible about the proposal. Although, 2 things I see that are a concern:

1) Does the spell fizzle as soon as you press it or at the end of the cast? If it fizzles as soon as you press the button, it could be annoying if you misclick a GCD heal and queue it up which causes a fizzle.

2) Wouldn't it be better to have a 1s recast native to Cleric Stance? One of the biggest problems Cleric Stance had back then was that you could immediately toggle it back on after turning it off, a 1s recast wouldn't hurt at all since you'd only turn it off to cast a GCD heal and every GCD heal already has a recast of 2.5s base (Eukrasia + Prognosis/Diagnosis is 1+1.5).