Have you tried managing a lot of Pokemon in Pokemon Go? How is your experience so far? Any lags or frozen menu? Personally I have a Sony Xperia Z5 which is more than decent enough to run the most demanding mobile apps but for Pokemon Go, things just get frustrating when you try to transfer Pokemon or do upgrades, and other Pokemon management tasks.
Sure, the game is a hit, no argument there, but managing your Pokemon inventory via the mobile app itself can be frustrating. I stumbled upon this article from Otakukart.com and I agree with it. Niantic should create a web-based application or an online portal which allows its Pokemon Go players to manage their Pokemon and items on a computer where frustrations on freezing menus don't exist (well maybe for some older computers.)
I also searched online for third-party portals and applications and found PokeNurse, a computer program that can connect to your Pokemon Go account and lets you manage your inventory. The only problem with unofficial applications is that Niantic can drop the ban hammer anytime.
Why Niantic should make a separate online app?
Since Niantic has been dropping ban hammers left to right, it would be better if the app would come from them. The data would be more secure and cheaters can easily be caught. Having an official portal or web-based application is also an opportunity to sell something that isn't in the app, perhaps an extra locker room for hoarded items?
Why does it need to be a separate application or portal?
As you can observe, the client-to-server transactions in Pokemon Go is way too high for a mobile application to handle. In effect, the app freezes from time to time since it has to communicate to the server often to confirm data. This is why when you manage your Pokemon, the menus freeze and you have to be patient about it.
Even healing or reviving your Pokemon takes a lot of time and even a lot more patience. I observed that it takes around 3 seconds for the revive or potion to reflect its effects on the Pokemon and I'm using a Sony flagship Xperia Z5. I initially thought there wouldn't be any problems, but I find myself spending a lot of time healing and reviving before getting back into gym for some more battles. Why not stage a mobile site for it and have it run on an exclusive server for transactions? This way, players can choose to do their Pokemon management at home (like homework), when not playing.
What particular actions can be done on this proposed web application?
Managing your Pokemon in Pokemon Go, as said a lot of times, is frustrating due to hang ups and frozen menu. The goal of the web app is only to manage the Pokemon particularly: Powering up, Evolving, and Transferring. And maybe later on, allow this web based app for trading and other non-gaming tasks you need to do.
Do you need to go home to a computer to do this?
No, as described above, a web-based mobile app is used on browsers. You can do this on a computer with the convenience of a mouse and keyboard but you can also this via your phone's browser. The transaction would be a lot faster since you are not running the app as a whole but rather you are just communicating to the server with the necessary data for managing your Pokemon.