I don't like grinding so I planned to gather the required commodities and materials whenever I encounter them while smuggling, hauling, exploring, fighting, etc. It'll probably take a long time until I'm ready to go to an Engineer. I like combat and I often end an evening's playing session by jumping in a combat ship to go fight at a RES or Nav Beacon or interdicting NPCs. This is impossible now. I have 8 tons of stuff for Engineers in my Python after doing missions. I'd like to keep that stuff for "later" but now I can't switch to a combat ship (they have 0 cargo space of course). The Engineers' bases are too far away from my home system to drop off the gathered stuff and then fly back to switch to a combat ship. And even then I would be forced to dump the stuff I don't need now but do need for higher tier mods I want in the future.
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This is a serious oversight by someone at FDEV. Cargo and module storage should have been part of the 2.1 Engineers release.