Ok, I'll bite.
How does this union work?
How many microstock photographers are actively contributing content in today's market?
How many do you expect to join your union?
How are you going to bring them together?
Who sets the cost of images?
How does membership work?
How much does it cost?
Are there any other benefits besides collective bargaining?
How are you going to set prices so your union members make more money?
Why will the stock agencies buy from your union?
What are you going to do about all the photographers that don't join your union who are willing to sell their images for 20% less than you, undercutting your market, taking all of your customers and putting your union out of business?
Get back to me with some answers. If you haven't given these and many other questions any thought, you're just blowing smoke.
1. legal entity as board commission
2. stock agency in front of that
3. at least 500.000 global
4. incentive, high return per sale, idea that their opinion matters
5.motuh to mouth, social media, (force

6. union behind the agency by vote. 1$ 1 point, you pay 1000$ a year you have 1000 available points
7.like everything, with $ (How does membership work?)
8. it costs what you are willing to pay. eventually close to nothing 0.0000001% for maintenance maybe for a gym aka shutterstock, hammoks apple ...
9.dedicated photographers will be rising above iphone era with their creations not their tools
10. smartpone photographers are welcomme to join (side note)
11. leave the prices where they are, todays prices are ok for buyers and seller, commissions to producers isthe main complain
12. agencies are sellers not buyers! you cut them off completely, hardest thing to do (not impossible!)
13. union is the business, we take them out not vice versa
Some other important aspects you forgot to mention
communication channels must be setup initially
we are already having this discussion inside of a union (this forum, global effort that should not be forgotten)
someone somewhere should assume responsibility for the first steps
some of us should take the risk and bet some money. legal framework i believe will be expensive for a person but cheaper for few of us together
term union i find it to be old, meaningless and scary for the old timers, lets address it collective business (will affects russian contributors)
wpo is dying or already dead or in the pockets of corporations, but they still may have something to say( experience at least)
i am thinking of a great example of our times, living proof that communities, even virtual one are very powerful
in the rc world (drones) open source communities are beating the crap out of corporations
If my arguments have any impact on you feel free to reply
and yes we should blow some smoke
Best regards, Jack