I had a discussion with R&D back in January this year. Here is what they shared:
From R81.20 we support min slave feature when you can configure how many slaves should be UP in order to the bond to be UP (cluster grade wise).
For example if you have 3 slaves, you can configure that the min slaves should be 3, therefore if one slave is down, the bond will monitored as down in cluster grade which will trigger failover.
You can define it in gclish:
set chassis high-availability bond <bond_name> min_slaves <value>
Installing policy after.
Monitor via:
cphaprob show_bond