The stock wifiwave2 package will never work on hap ac2 due to storage constraints. I think theoretically Mt should be able to release a stripped down package which only includes the necessary drivers for this model. But even then, there is still the issue that most hap ac2 models only have 128MB RAM, so Mt might have to tune some buffer sizes to prevent crashes.
Tl;dr: Theoretically possible, but I wouldn’t count on it.
I realize that even under OpenWRT the firmware is stripped down to fit low RAM of 128MB.
So I am reselling my 3 x hap AC2 today and I purchased an hap AX3 for testing.