SSL Has anyone setup an SSL Redirect Farm?

You could bulk add all domains to Cloudflare via Cloudflare API for DNS and proxy/CDN management and then use Cloudflare API to setup page rule redirects for How do I perform URL forwarding or redirects with Cloudflare? just need to use Cloudflare API to bulk on mass setup the pagerule.

What problems you having now ?

You mean for instance you have domain.net and domain2.net and domain3.net and domain4.net all redirecting to domain.com with

• non-https domain.net redirect to https domain.com
• https domain2.net redirect to https domain.com
• non-https domain3.net redirect to https domain.com
  
• https domain4.net redirect to https domain.com

Below all assume domain.com https target destination is already setup and working

redirect non-https domains listed in server_name directive to domain.com https site

Code (Text):

# for non-https domains all listed in server_name directive
# if unsure use return 302 temp before using return 301 permanent
server {
  listen 80;
  server_name domain.net www.domain.net domain2.net www.domain2.net domain3.net www.domain3.net domain4.net www.domain4.net;
  return 302 https://domain.com$request_uri;
}

redirect domain2.net https site to domain.com https site provided domain.net is already running Centmin Mod with letsencrypt SSL/https setup

Code (Text):

# each https domain i.e. domain2.net needs it's own letsncrypt
# ssl certificate and redirect via 302 temp first than later 301 permanent
server {
  listen 443 ssl http2;
  server_name domain2.net www.domain2.net;

  ssl_dhparam /usr/local/nginx/conf/ssl/domain2.net/dhparam.pem;
  ssl_certificate      /usr/local/nginx/conf/ssl/domain2.net/domain2.net.crt;
  ssl_certificate_key  /usr/local/nginx/conf/ssl/domain2.net/domain2.net.key;
  include /usr/local/nginx/conf/ssl_include.conf;

  return 302 https://domain.com$request_uri;
}

redirect domain4.net https site to domain.com https site provided domain.net is already running Centmin Mod with letsencrypt SSL/https setup

Code (Text):

# each https domain i.e. domain4.net needs it's own letsncrypt
# ssl certificate and redirect via 302 temp first than later 301 permanent
server {
  listen 443 ssl http2;
  server_name domain4.net www.domain4.net;

  ssl_dhparam /usr/local/nginx/conf/ssl/domain4.net/dhparam.pem;
  ssl_certificate      /usr/local/nginx/conf/ssl/domain4.net/domain4.net.crt;
  ssl_certificate_key  /usr/local/nginx/conf/ssl/domain4.net/domain4.net.key;
  include /usr/local/nginx/conf/ssl_include.conf;

  return 302 https://domain.com$request_uri;
}

FYI, you can bulk add Centmin Mod Nginx vhosts via tips and nv command line outlined at [Guide] Save time creating Nginx vhost & MySQL users and databases too with or without Letsencrypt SSL cert and HTTP/2 HTTPS.

It's fairly easy to just write a script if you know how to automate generation of above Nginx vhost configs for non-https to domain.com and https to domain.com redirects combined with nv command line bulk creation of domains on a single server if they currently don't have a home/server. Of course more tricky if the domains are already existing sites on their own servers, in which case you'd have to modify them on server level if not via Cloudflare method I outlined early at DNS and Cloudflare API level.