If that's the price to pay for 'actually interesting gameplay during downtime where there's nothing to heal' I'll absolutely make that trade. The issue is that SE would do the first half of the trade (instantcast, free heal GCDs) and not the second half in compensation (the additional gameplay). See Kaiten, and how some expected it to be replaced by something else that requires braincells. Instead it was replaced with... nothing. So the kenki got dumped onto Shinten instead, very fun.
And if the change did happen in such a way that eg Medica is now an OGCD with a 2 sec CD, what would the new rationalization from the 'healers should heal' squad be, it's not like the 'casuals' would be stressed if they could weave healing OGCD at literally any moment, akin to weaving tank mitigations