- being able to link to individual sections and their subpages
- resizing the iframe dynamically
While looking for a solution, I discovered that Github pages, where the website is hosted, supports Jekyll, which is a mechanism for generating static pages from templates.
The new interface now uses vertical tabs (the design needs to be polished, I admit), that make the whole site display better on the smartphone, and I no longer need a special navigation-less in-app display.
The added advantage: MyExpenses now can call Android's browser for displaying content and no longer relies on its own Webview, thus no longer needs the permission to access the Internet, which understandably is a stumbling block for security sensitive users when dealing with a financial application.