I guess I don't really understand how this works although I admit to not reading everything. Most SaaS companies are very vigilant about not having per-customer code changes - many people have lived through the hell of ending up with divergent code bases as a result of customer demands.
But I did want to mention something that I think would work well for SaaS companies which is related, and that is empowering customers to make their own changes to the core product.
We tried at one stage having a council of customers, but it's simply wasn't practical to implement all of the ideas that they came up with. That's changed now.
I think an interesting product would bundle the communications, voting (if necessary), updates, screen captures / video demos, feedback loops and so on that are involved in a decent sized group of customers consolidating their requirements/ideas.
A true mark of success might be when the product becomes self-stewarding, with customers driving a lot of the requirements.
Our solution to that age old problem is to scope each new feature into its independent "app", which is sandboxed and walled off from the main source code