FCs' mechanics need to get more efficient as far as fueling and traveling is concerned, but a phone app is not the way imho. It opens a dangerous Pandora's box for other grindy and compulsive situations found in some games with such an app.
Fdev doesn't even need to develop it honestly. Since Fdev has the API, they just need to enable it to go both ways for just carrier stuff, and the community can develop the app. I mean they've developed several apps already using the API. I remember the fan made Destiny app that allowed you to manage your storage in much the same thing, which was interesting. EvE has plenty of third-party apps.
I know your worried about some kind of mobile grind-y mechanics being created but honestly, that's more a reflection on Fdev's design mandate (which they don't seem to want to do) rather than simply enabling the technology.
Since Fleet Carriers are this persistent asset that exists regardless of the player is logged in, they really DO need some kind of external management, whether it be an app or a sub-page on the frontier site or third party site, something.
And the use case I can think of is exactly what a lot of people, myself included have encountered, being away from home at work or out, and the carrier needs to be moved, refueled or the market orders changed, etc while your squadmates are online.
It would be a convenience of having the contents of the carrier management screen that is accessible outside of the game, which I see as having very little to no downside.
