This is a quite an interesting architecture that could also be used for developing on the browser. I imagine some of the existing browser development tools use something similar
For my personal site, I switched to Marijn Haverbeke's Heckle <https://marijnhaverbeke.nl/blog/heckle.html> several years ago. I realized that I could pretty easily do a rewrite that uses my browser's native JS engine + browser APIs instead of requiring NodeJS and depending on the slipshod fragility of the NPM ecosystem. The result is triickl:
What's more is that, because I also created some tools that allow triickl (and similar programs) to be packed into a single, self-contained file that can run in the browser (e.g. buildfoo.html or pages.app.htm), it's pretty natural to let there be a page on the target site corresponding to this file. The end result is that if you're using triickl, you can clone the site's source repo and then use buildfoo.html to generate the static assets. In other words, so long as you're able to get your hands on the source tree, then every computer is already a development system.
It's so common to open apps from the search bar (and the app drawer now, I imagine), that it probably becomes less of a burden. Might even make people use those other patterns more, who knows.
It's early days for Mainframe. I agree it's still finicky, and I'm working to change that. What made you feel that way about it?
Feel free to reply here or email me. You can reach me through andre [at] mainframe's domain.