Instead of I & II together on a single GBA cart and III on the DS and IV, V, and VI on separate GBA carts, I would've preferred I-III on one GBA cart and IV-VI on one DS card.
I like things in trilogies, and these were originally in "trilogies" of sorts by console, meaning they have the proper buttons. I-III (from the NES/Famicom) don't need more than two face buttons so it fits on the GBA (though there are also two shoulder buttons) and IV-VI (from the Super NES/Super Famicom) don't need more than four face buttons and two shoulder buttons so it fits on the DS. This also means that all six main 2D FF games could be carried around all at once!
But of course that's only ideal for the consumer, Square probably makes a lot more money doing it the way they actually have it. Maybe they could rerelease them in the way I would like (if people want a DS-featureless III) afterwards and make more money... >_>
While I'm throwing out ideas, I think there should be a Revolution compilation of VII-IX that, through DS connectivity, if all nine games are complete (!), unlock something really cool. That'll prove who the REAL FF fans are.
VII-IX may be possible on the DS. I personally think FF VII is way overrated, but hey, I'm sure it would sell well if it were rereleased on something as popular as the DS.