Matthew, I see your point and those are all interesting ideas. I think it is worth exploring ways to improve the Connects feature in general for example. I don't know what the answer may be there but seems like there is certainly potential for improvement.
When it comes to incentivizing clients to hire more, I think that at the end of the day, there are so many reasons why a client decides not to move forward even if a system like that was in place. Again, they might have found a freelancer on another platform, maybe they realized that the project is going to cost them too much, maybe they had internal discussions with their team and realized there is a better way to solve their problem, etc.
I think no matter what you have to just keep submitting proposals until you get a bite. Sometimes that may take 1 proposal and sometimes it can take 50. Even freelancers with awesome portfolios and lots of good client feedback have to submit many proposals before they get new jobs (for the possible reasons I stated above). I don't know if that can be avoided. So that's why I said "that's the reality of freelancing".
