I wish that the features of web engines were more compartmentalized. The "convenience" of a Thing That Does Everything will also introduce fragility and bloat (and maybe even security exposures).
For example, I would probably love to call functions to lay out some rectangles for me. I know a web engine can do that really well, and I don't even mind passing in CSS strings to describe what I want. The problem is, I don't want "Internet in a box" to come with it; I just want the layout in that case. It would also be a lot easier to identify problems and contribute solutions if there was a way to "only" do X and focus on that part of the engine to fix.
It would be awesome to be able to take those kinds of low-level details, and start really going cross-platform with them. Make a library that can finally lay out whatever the hell you want consistently across machines, that can be patched into all existing UI libraries or other tools. Make a portable text rendering and text layout system. Make a portable GL viewer. But don't tell me that each of those things only works if I create an InternetInBoxView. Instead, refactor InternetInBoxView to use those separate parts.