<object> used like this is just a poor iframe in a much shakier spot in the standards, mostly for backwards compatibility.
Like iframe, it "includes" a full subdocument as a block element, which isn't quite what the OP is hinting at.
It’s an option built into html.
The OP doesn’t need to hint.
Sound like it's good enough for headers and footers, which is 80% of what people need.