To trigger a rebuild, you first need to know relevant upstream updates. To recognize them, you need to know your dependencies. Docker provides no means to track dependencies. In fact, avoiding dependency knowledge is one of its major selling points.
I wont say it's impossible problem to tackle. But I doubt any solution you find could work better or be less complicated then regular packaging. Unlike docker, debhelper, rpm, ebuild and others were designed for this task, and have decades of experience in the field.
