Shun/Neko
Do you play any moba games, what kinda game would you make with Cipher's assets if you have done so?
40%-50%+ of my gaming is through mobage and handhelds now.
Really what they would have to do is find a way to cut themselves out of the competition.
They can't do a direct port of Cipher to iOS because of card sales but they might when it starts to die down.
They can't just do a straight up card battle system like iM@S or SQEX mobage does since the characters in FE don't hold as much IP power.
How I would do it is find a compromise between how they did it for Fate Grand/Order, Chain Chronicle, Final Fantasy Grandmasters and GranBlue Fantasy in terms of gameplay.
There are so many characters in FE that you can keep doing frequent events to pull in more users and keep existing users. It's why iDOLM@STER Cinderella Girls Starlight Stage has been doing so well. They reused assets from previous games and do an almost weekly-biweekly event for new cards.
It doesn't get tired or boring because there is always an event going on.
In the case of chain chronicle and granblue, they have collaborations rather than straight up event asset reuse.
In Fate Grand Order they have events like Saber Wars where it's ONLY Saber cards because Saber is popular and the fate series is a ton of story bs. They could do Marth Wars or Lords only and Pegasus only events. There is a lot of potential for FE mobage.