I came across this idea whilst browsing through the Instagram / Facebook API docs and while I did find them to be much more limiting now than they used to be, I came across an idea that would be useful for me - and so hopefully other will find it useful too.
I built the back-end using nodejs, and the front-end using vuejs. Once built I applied for the required permissions through the Facebook graph API, and got 3/4 which was enough for what I needed to do!
I integrated stripe to handle the subscriptions and have set a 30 day free trial, with no commitment so the barrier to entry is very low. Hopefully I can get some people in there to see what they think!
Total cost so far is around $100, which is basically just the domain name + business registration.
The website is now live, and anyone can signup - so now it's time to do some marketing!