Like @encoderer and Cronitor.io, we also stuck with Django 1.6 for several years! YAY! Turns out the jump from 1.6 to 1.7 was a painful experience, but we're finally on the modern.... 1.11. Yeah, we're not getting rid of our Python 2.7 customers for some time (still trying to get some off of Python 2.6). Enterprise software development is a different sort of beast.
Our https://rbcommons.com service is Review Board as a SaaS, and uses Stripe. Curious to hear what you're doing with Stripe integration on your end! We've been making heavy use of it ourselves.
We've also done some crazy, fairly-complex, maybe-niche stuff in Django, and built these out into some libraries you might find interesting to browse through:
1) Djblets (https://github.com/djblets/djblets) — A big ol' utility library for Django that provides:
* Foundations for loadable extensions (just like browser extensions) for Django projects
* Support for defining flexible integrations for third-party services (Slack, etc.)
* Avatar support (gravatars, file uploads, URL-based avatars, and custom backends)
* Datagrids (with user column customization)
* A foundation for REST APIs
* Dynamic site settings
* Stuff to make privacy/PII/consent a first-class citizen in codebases
* And just a ton of other things that we found useful in Review Board and wanted to make more widely-available.
2) Django Evolution (https://github.com/beanbaginc/django-evolution) — A precursor to Django's migrations support (and the reason we were on Django 1.6 for so long — the in-development version cooperates with migrations now). We inherited and maintain this project. It provides an alternate way to specify database schema changes, and has the benefit of just being far faster to apply migrations, through a built-in optimizer. This significantly reduces upgrade times for large installs (super important for many of our Review Board customers).
All open source, and might be interesting to look at, who knows. We've built a lot up over the years (we started by writing code against Django pre-1.0 SVN checkouts), and I still recommend it.