No way - you will by 100% get an system with already known issues!
Blackview doesn't care about the issues because you already bought the phone...
I'm sure by 100% that any Android 7 update will be released with the "root bug" not allowing to run banking and other security software because the system image still has the test-keys labeling.
you say all this but they are not required to update the phone at all, the fact they are updating proves they care, as for the bug, its there as blackview use a 3rd party to create the roms.
Even if you use 3rd party the developres should follow Android development procedures - not eliminating such a Kindergarden error but stating it is taken care of in the next release or in the current release and you should update is just b*llshitt!
If any mobile phone company doesn't provide updates they will be out of the market within days
as for bugs in software the users demand security fixes at least.