I would think most healers would actually love a visual representation of just how much damage absorption the tank currently has. They'd be able to much more easily tell when they have some breathing room. All it would have to do is combine all current damage absorption values and display that as a blue bar over the tank's HP bar indicating what percentage of their total HP is currently shielded.
As for the console memory limitations: this one might actually be doable since it's modifying an element that already exists rather than adding a new one. The only new data for each client to store would be the total shield health for each party member so I suppose it'd be in the same situation as the party TP bars. They've managed to find room to give us those TP bars so they may be able to give us this one as well.