My goodness 15 resources?! You're mad, you know!
You're supposed to run an entire empire, not a company. This creates too much micromanagement. I sympathise with Aaron, he gave the modding community 2 extra resource possibilities. That should be enough for 90% of the community. The remaining 10%... tough luck.
I can imagine something like:
"I want to build this All-Consuming-Ship-Devouring weapon on my precious Eater-Of-Worlds-Ship, unfortunately I can't build it because I haven't found enough solarsteel and biocrystals. Oh damn, I also lack some trifflefluffy and gummiberenbessensap."
Okay, I made a bit of a joke of this, but it reflects the comming doom of 15 different resources. I stick with three or four different resources, more than enough for me. I'm one of the 90%...
Edit:
Rectified a small error in gummiberenbessensap.