Yes, I'm pretty sure everyone knows that Hull C/D/E can't land planet side (or in hangars). But this just means Hull C is designed to cut the most arduous part of a traditional trade run: the part where you land on planets (or in hangars). Honestly, that's not really a downside. And sure, you'd think that if you do the space lift part yourself as well, you'd maybe earn slightly more, but we've seen some station-to-station items that already were part of the most profitable trade runs. Everything is subject to tweaks though.
(As for when we're going to see it in game, there's actually already cargo you can trade between stations and rest stops. However, I'd say Hull C requires something like a very special hangar or maybe a docking port next to a cargo platform, so yeah, I'm not expecting it in 3.18 either)
Nor would I characterize this 32 SCU box thing as an "expense." 4608 divided by 32 is 144. You can still haul 144 different types of goods onboard of a Hull C at the same time. And that's assuming you can't combine different types of goods into an 32 SCU container, which might actually be possible. On a side note, the most variety I've had on a trade run so far was less than 10 different good types.
I mean, sure, anything is possible. But I'd give Hull C getting $50 to $100 flight-ready price bump far greater chances of happening than the price bump being the normal $10 to $20. And I mean, if we're speculating on CCUs that could bring good deal of benefits, then that's certainly one to speculate on. Still, if you had to choose between Hull C, Crucible and Endeavor, I'd go with Endeavor, then Crucible, then Hull C.