Chris,
I have a way in which you can prevent vendors from being able to list a product unless they have connected a Stripe account in their pro dashboard > settings > payments.
It shows a message that tells them to connect to Stripe, and a link to the dashboard settings.

In order to use this, you’ll need to modify the product-edit.php template.
move this template: wp-content/plugins/wcvendors-pro/templates/dashboard/product-edit.php to your theme or child theme.
I think you’re using OneSocial???
If so, for onesocial you would move it to: wp-content/themes/onesocial-child/bb-marketplace/wc-vendors/dashboard/product-edit.php
If not, then: wp-content/themes/your-theme-or-child-theme/wc-vendors/dashboard/product-edit.php

You can replace the entire file with this, or add the parts I have added, as I’ll explain below what’s been modified so you can add the modification again to the template the future if we have to update the product-edit.php:
https://gist.github.com/fervous/29305b1e2eae55dec22eaec32bb1adef

First change:
lines 24-28, I added this, which checks for the Stripe token of the vendor. If the token exists, then no worries- it shows the product add/edit page:

$access_token = get_user_meta( get_current_user_id(), '_stripe_connect_access_key', true );
if ( !empty( $access_token ) ) {
?>

Second change:
After , I added this, which shows this message and blocks the product page from showing if the Stripe token is not found:

<?php
} else {
echo '  <p><strong>WAIT!</strong>   Before you can add products, you must connect to STRIPE, so you can receive the funds from your sales.  To connect to Stripe, <a href="/pro_dashboard/settings/"><strong>VISIT YOUR STORE DASHBOARD SETTINGS</strong></a> and click the <strong>PAYMENTS</strong> tab.</p>';
}
?>

I use this on my own site- works great.

When I gave you the file path yesterday I forgot to add the bb-marketplace to the path for the OneSocial theme– make sure you add that in and this should work.

Sorry!

@fervous toss that in a kb article =)