I know you say you don't want to make this about pre-existing conditions, but if ACA is repealed without a replacement plan which guarantees coverage of pre-existing conditions, then you can't ignore that in this conversation.
The thing is, I'm a perfectly healthy person, maybe 5 pounds overweight, no ongoing prescriptions outside of birth control, and no health conditions. But before ACA, my parent's (they have been privately insured my entire life) insurance did not cover any medical costs above my shoulders. I had a one-off seizure in 2009 with clean EKG, clean EEG, clean CT, clean MRI, and no further seizures in the 8 years since. When I had migraines in 2010, they wouldn't cover doctor's visit or meds for it or chiropractic visit which really helped relieve the debilitating migraines.
You have to remember that pre-existing conditions are defined by insurance companies. If ACA goes away and it goes back to that, they may deny you coverage for any number of ridiculous supposed pre-existing signs. Despite the fact that I definitely did not have a brain tumor at that time, if I'd developed something like that before/without ACA, the insurance simply would not have covered any of my care.
It sounds like this option might work for your family currently. But I don't think anyone can say with any certainty what our insurance markets will look like in 6 or 12 months. Most of this conversation is YMMV based on your risk tolerance to political and insurance changes as well as the level of insurance you feel comfortable with.