If they want balance while retaining Job identity, they need to figure out the absolutely necessary buttons and make them Role Actions. Then use the rest of kit to have a different flavor of approach to DPS and utility. This doesn't mean all the role spesific things need to be cut from the Job, it's fine if they still have some of their own approach to healing and tanking but it would be easier to balance and make even more flashy as long as the core is there and sufficient.

It might homogenize Tank and Healer core roles (though you could argue they are already fairly similar) but it would allow for more freedom elsewhere making them fill their roles while having a better Job "fantasy".

Another thing that I like to bring up is also making the Tank and Healer roles use more supportive feedback loop. Some of them at lower level completely skip mitigation or damage while focusing almost solely on damage at high level. It would be a simple thing to add something like basic attacks building your healing / mitigation big button and properly healing/shielding/regening/mitigating etc. etc. in turn giving you flashy DPS button(s). They can even fight button bloat by having a dedicated button or two that changes depending on what you have built up.