Great question! We've already built an Amazon integration that lets office managers convert employees requests into direct purchases on Amazon. And we plan to build many more in the future.
You guys are on the right track, but eventually you're going to hit a wall where you'll need some serious maturity with procure-to-pay.
I'm not sure how the tone of this comes across, or if it's in any way negative because you guys are onto something... but have a lot of competition that is often deeply integrated (see Service-Now catalogs for example).