For me personally, engineering is what keeps me from buying more ships. There's a good handful of ships I would like to have for various purposes (instead of swapping modules all the time) and I'd also like to fly some of the smaller ships for a change of pace and their different feel. But the effort of getting them engineered up makes me just stick to my all 100% G5 Anaconda for everything, because I honestly cannot be bothered.
What I would like, is if you only had to do the G1 => G5 100% progress once per upgrade and then could buy the same upgrade again and again for additional modules just paying credits. Basically you'd give the engineer a wide selection of materials so they can experiment with module upgrades until they figured how the get the most of of the module. Afterwards they know how to do it, so they can reproduce the same upgrade for a lot less materials - which they can also order on the market, because now they know what they need.
They way it is right now, the engineer suffers retrograde amnesia the moment they finished a module and have to figure it all out from scratch again, if you need another one of the same. But they also work entirely for free, once you paid the initial unlock of their workshop. This doesn't even make logical sense, even if it was good gameplay.