The trouble with "Let's build out a handful of integrations. Make sure they're going to deliver the value we want. Then abstract it into a repeatable pattern" is that when you're building an integration marketplace, you need partners, and they don't want to be your research bitches.
They just want to build their integrations once, and gtfo. If they think you're signing then up for a revolving wheel of experimentation, they'll just politely stay away until someone else has done the hard yards.
Sure if you're a Microsoft or a Google you'll have any number of willing partners who will put up with anything to be the pioneers in your integrations marketplace.
But otherwise, they're using your integrations marketplace purely for the benefits, and they don't want to be building on sand.
I would argue this is a case of over-engineering. Though, it extends beyond pure engineering.
This is poor resource management and business de-risking. An effective approach here would have been: "Let's build out a handful of integrations. Make sure they're going to deliver the value we want. Then abstract it into a repeatable pattern".