First of all, I HIGHLY doubt that they'll bother to port the game to the DS unchanged (content-wise). That's just not their thing for the DQ series. So we'll probably get new items and a more fleshed-out equipment system, a couple of new bosses and monsters, a couple of new dungeons, and possibly even a new story scenario after the main game. THAT'S much more their style when remaking DQs.
That said, I still think you're dead wrong about portability not counting as a feature. I've attempted to play through DQVII 3 or 4 times since I bought it, and never got past the 40 or 50 hour mark. Pop it onto the PSP and bam, a near-140 hour clear file that's only an hour or two from finishing the second (and final) bonus dungeon. Hell, once I finish this last dungeon, I'll also have a complete monster book. It's by no means a 100% file, but it's reasonably close. (All human classes mastered, all tinymedal prizes redeemed, monster park fully expanded, etc.)
So yeah, portability had a DRASTIC effect on my overall play experience. It was, for all intents and purposes, a game-making addition, or feature, if you will. The lack of such a feature on the PSOne was effectively game-breaking to me. But, as I said before, this is quite subjective. If one doesn't spend 2+ hours commuting on a subway/train/bus, each day, then yeah, not a big deal.