Well, first of all, I'm a huge FFIV fan. It's my favorite of the series.
While I'm disappointed that it's being released for mobile, I really can't blame Square-Enix (of Japan) for doing it. Pretty much everyone in Japan owns a mobile phone, and NTT DoCoMo has a huge monopoly on the mobile market there, so pretty much everyone is on the same (highly advanced) mobile network, and pretty much everyone is using FOMA iMode phones, because DoCoMo releases a ton of different models at different price ranges for all of their lines. So there is huge market penetration for these iMode mobile games, which is why Square and Capcom and Konami and, well, every Japanese publisher is taking advantage of it. On top of that, it gives them an opportunity to use a smaller staff and budget (though, it's hard to say if they're that much smaller than DS, with mobile graphics over there already catching up to the PSP).
Unfortunately, anyone outside of Japan gets kinda screwed over, because our mobile technology is nowhere near as advanced, stable, or homogonized as it is over there.
I mean, in a business sense, and even for Japanese consumers, it's a good deal. I'm sure many people will play it, just like many people play their other mobile games.
Square-Enix of (everywhere else) just need to figure out how to distribute these games to everyone else, if not by mobile, than maybe via PC, or ported to console with other games (the MG1 and MG2 ports with MGS3 were ported from the mobile remakes, for examle).
Oh well, for the time being, I'll just have to read Japanese scripts and watch videos on Nico Nico Douga. :/