I've been developing my skills, so I'd like to ask, what kind of web app would you want to exist if someone could make it happen? Though you can also suggest non-web apps, or mobile apps.
It doesn't have to be pokemon related of course. This will be a thread of free ideas for anyone to take and try and design it themselves! Use it as a challenge or a way to learn.
Back when I was still into competitive I came up with this idea of an offline backup system for Pokemon Showdown teams. You could load up the tool, hit backup and it would simply extract the data from your browser and store it into a local database. Then you could take the data, put it into another computer, hit restore and it would install your teams to that browser.
That tool was also meant to serve as an organizer. You could view teams, modify them and even remove entire teams. It would also allow you to export them into different formats. For example you could get the normal Showdown text format, or the pkm format that is used in the actual games.
Second thing that I came up with, but never did anything with: a module based editor for ROM hacking. It was meant to unify all the ROM hacking tools for Pokemon games, that have been floating around forever. That idea came up because I simply could not understand why people still accept using tons of different tools instead of someone actually putting them together into one single editor. Every tool and every patch was meant to be incorporated in form of a module, so it was supposed to be pretty customizable. You would only need people to create their modifications in a certain way and then you could just put it into the plugin folder and your ROM would always get patched with that functionality.
Both of which are pretty hugh undertakings which is one of the reasons I never got around doing any of it.