Looks like selling an item won't be too much of an issue. It's a pain to work with the inventory as they do something obtuse where the actual bagslot stores information about an items collectability, durability, soulbound etc. And it's because of this that they don't want to give us more bag space and that when you insert items into your armoire that they loose all this extra information and just become item ids.
But on another note, Mastahg. I did notice you were able to get convert to materia working earlier in RB. I assume it must be somewhat similar for aetherial reduction and desynth. Would it be possible for you to share any information on how you got convert to work? I would be willing to use that and figure out how to do the other 2.
You can now sell items via CommonTasks.SellItem