Well I won't miss this, largely because I haven't used it yet.. and I typically just sell those weird cargo items anyways. It's only been recently that I've even starting making upgrades and haven't progressed any beyond 2nd rank, but this will improve the upgrading process.
However... I have been "At Capacity", with 1000/1000 materials in my Materials Holding Compartment, or where ever those things are stored, for quite some time. And while it's not really an issue for me to dump a stack of materials I have a lot of, in favor of something new, useful, or simply need more of, it would be great if we had a means to sell off, trade or utilize these things for something more than just Engineer upgrades, to make them a little more valuable - or we had a means of converting them either into a cargo commodity that could then be sold or traded normally, and of course, a means to reverse that process as well.
For example, if I happen to have, as is not entirely uncommon, 100 iron stored away converting 100 iron into 1 1-ton Iron commodity, or by reverse, converting a 1-ton Iron commodity into 100 Iron Materials.
This would allow for more mission variety, more trade opportunity, and make these materials more useful to everyone.
How so? Let's say you're a miner who has just landed at some small outpost that is trying to grow. In addition to the usual missions, being able to do this would now allow for missions like:
Outpost Needs 2 Tons of Iron or Outpost Needs 4 tons of Niobium
So you set off to track this stuff down, perhaps in the case of Niobium, in an SRV across the planet's surface, hunting for Chondrides or Meteroites to locate these. After gathering 400 Niobium you then convert them into standard Cargo, which can then be exchanged to complete the mission, gaining Rep++, Inf++, Credits, and helping the outpost grow.
And more importantly, it helps empty out your Material Storage in a more useful manner than simply jettisoning this stuff out into space.
Or on the flip side, you know you're going deep into space, far from civilization, perhaps to the opposite side of the galaxy itself, so before heading out you pick up a couple 1-ton Cargo containers of Arsenic, Niobium, Yttrium and Polonium, knowing these materials can be used to generate much further FDS jumps than normal, so that you can not only make the trip out, but back, in considerably less time by converting these into 100 Materials each.