Here are a few things I'd like to see for GURPS.
- I'd really like to see some additional sourcebooks on Japan. We have GURPS Japan, which is Edo-period with some supernatural stuff thrown in. It's fine, but my first interest in actual Japanese history sprung out of the game Nobunaga's Ambition by Koei, which takes place in the Sengokujidai.
Before that you have all of the bloody battles and political fights of the Heian period, the war between the Minamoto and Taira, the legends of Benkei and Yoshitsune, etc. All the good stuff that happened long before Sekigahara in 1600 effectively unified Japan.
I'd be happy to write this stuff but I can't read sufficient Japanese to tackle historical research with any kind of speed. So it's better that I act as a peer reviewer than a solo author.
- GURPS Martial Arts support, with new styles or with campaign settings much like Gladiators. I could write this stuff if I didn't basically have a full time job and a half, which kills a lot of my time for research.
- Short DF Adventures like 2-Page Dungeons, soon to be released. Again, I'm not the ideal author for this, but it's useful stuff to have and I'd be willing to support it with my money and time.