Hello Commander Almondclint!
I think it's unlikely that we will allow the purchase of materials. They exist specifically as a new resource to manage.
That does not invalidate your complaint, of course, so things that we might look into could be: trade materials for higher class or different types at material broker contacts (probably at some loss), tweak the algorithms so that materials for pinned blueprints had better chances of being generated, more rewards that were materials based.
Trading sounds good, I'd suggest trading one high grade material for another though, not lower class for higher class.
That'd lead to some odd, probably unintended things.
For example, i can find 100s of Focus Crystals if i want, with no effort (just have a limpet or two follow you around a RES).
If i can trade those up for Refined Focus Crystals, then trade those up for Exquisite Focus Crystals, it'll kinda ruin the whole "rare" thing.
It'll just become farming low grade materials, then swapping for high grade.
I did suggest a negotiation idea a while back, so you can "reroll" your current reward, or increase your current reward, at the cost of other things, like cash, rep, influence, etc (and negotiate with the other rewards too)
I'll see if i can find it.
Edit: found it!
Mission Reward Negotiations
CMDR Cosmic Spacehead