Yes, I do think it could be quite useful. Although the basics we have so far are already quite useful and cover many cases.
Yes, that would indeed work! And since I think we know that they are implementing hidden fields, if more sophisticated filtering does not come, or comes later, then once hidden fields are available you could use this method without cluttering things up.
Yes, very important here as well! I hate to admit it, but some tasks do just sit there for ages (sometimes by design, other times… )