These signup cards look great, thanks!
What I’m wondering is whether or not there could be any issues if I were to copy the outputted HTML of one of these cards from the source code and place it into an HTML card. Or more specifically, I wouldn’t mind inserting that HTML into a script as I described in this comment so that I could use a snippet/template setup which would enable me to effect any possible changes on all signup cards used throughout the site at once. As far as I can tell my tests via an HTML card seem to work without any problems, including the signup card not appearing in the email preview (haven’t tried to see if that carries over to actual emails).