Would likely be possible ,although maybe requireing an actual UI for it, as extending your inventory might not be easily possible. The size is a bit small, although I could imagine a complete set (compresser helm, on the other hand, sounds like a bad idea, hmmm) but yes, I think it would be useful, and usable, especially as another alternate piece of armor. The main issue is that it competes with the OP nano-leggings, and considering that the opertunity cost is a bit high, I think bigger capacity is really required. I mean should I really pass up +6x (I think) movement speed for +25% inventory space? Its hard to say.
If it were a separate UI it would probably be easier to code, too... I had thought of this, but didn't want the added inventory space to be considered excessive, or imbalanced. This was the reasoning behind using the armor slot to limit the number of devices available at any one time to just one.
An alternative to using an Armor slot is to make the UI only available if the device is right-clicked while holding it; in this instance the device should still draw power even when inactive. Note that this would allow for multiple extra storage (with consequent increase in power drain).