Built-in Partial Page Rendering Capability for Site Integration

Seeking more cost-effective solution to integrate their existing (e-Commerce) websites.
Ideally, we want to have a built-in service or URL pattern to retrieve partial rendered HTML markups right away from the delivery tier without any complexity.
HST Component Rendering URL seems to give a similar result as 'partial' page, but its URL is transient and the reference component ID cannot be inferred by integrators, so it cannot be used easily. It would be nice if there is a transparent/consistent/solid URL pattern support for partial page rendering scenarios.