Ok, i will give it a try 
Let’s go.
First i want to collect all the facts, which are given to this problem.
- You have 1000-User-Website where you want to create a form, which can register 1000-user at once using a custom form.
- All neccessary data is given…
a) User-Email
b) Password
c) some other user-related data.
So all you want to achieve is the registration of these user in wix.
My little tricky “bypass-solution” would be the following
Take a look here…
https://russian-dima.wixsite.com/meinewebsite/automatic-registration
This little form-tool is able to register several user at once (but without e-mail confirmation).
How to use?
- You create a List of User which shall be registered (DEMO-list)…
- When the DEMOlist is ready, you have just to push the green button, to fullfil the registration of all USERS which are in the list. The result can be seen in the “Private-Member-Collection” -table. All users should be in the “Private-Members-Database”.
Attention! After running this procedure, you will just see the first registered user in the table, because you will be logged-in as this first user, right now.
To see the whole “Private-Member-Collection” -you have to log-in as site-owner!
Of course you may now say… —> ok and what is now the advantage of this, i can also register the users the same way of my own, one by another.
The advantage is, that you now are able to import a CSV-file to one of your custom-created-DATABASE (in this case —> “Member-Data-List” look at the first table) and then just press the green button! And that’s it 
No? I am wrong?
The result should be like this one from this example…
All USERS were added to “PrivateMembersData” by one button-click.