A lot have been said in the witness forum, good that you point out what’s important and make a call to action. 

My opinions:
>I think we should focus on growing the active blogger base until it's large enough to have more businesses 

Pretty important, I am running a business and well sell software, our business Plan was to build a customerbase by providing a lot of free modules to download, now that we got that, we started selling „better“ modules...

A point you didn’t mention was the rewarding system(nonlinear?), I think it should be fixed, also (bot) abuse and so on, before we can think about going to the moon 

The onboarding is a problem, but I don’t think that big as some other witnesses, people who want to join, will wait, like I did... no a primary problem 
To maintain the active users there should be good support, example: a wiki in each language, witnesssupport/watch 
Then make steamcleaners more attractive(community should clean itself)
Maybe an author council, or at least a testing

We have to try things to see what works and what not to grow and develop.