I've spent some time playing around with a M+ style script in the new healing system. I based the healing boss script on the current tanking one, but replaced some of the damage with group-wide aoe. The "ScaryNuke" from the 4 packs is now a mid-sized group aoe, and the BossSmash ability is as well. Also, the BossCharge ability selects a random target (Like the BRH boss i believe the original fight was modelled on).
One thing to keep in mind with this script is that you CANNOT use the default healing script and expect good results. I did not program in all of the AoE/tank/normal/light phase labels, and instead opted to just write a generic healing rotation script that should work for the entire encounter. I would consider this a very early beta-type demonstration of what is possible, but the gearing strategy it produced was very close to what I would expect for M+ (extremely high Mastery targets as a resto druid, then balanced Crit and Haste), so I think it's a good demonstration.
Here is a link to my M+ script. It's currently tuned to approximately what I would consider mildly dangerous damage levels (the tank's health can get a bit dicey sometimes).
Some limitations to consider in M+ sims is that there is a set amount of incoming damage to heal, and not other healers to manage it. That means that there is effectively a cap on the HPS you can produce, though I think the script will eat/drink between phases so there is some sensitivity. More thought would need to go into how to make the scenario more flexible to healing output before I'd strongly rely on results, but if you just want to get a look at what a mythic + healing sim might look like, feel free to play around with it.