More planet types like Water, Rock, Forest, Jungle, and Ecumenopolis are definitely needed, and Gas Giants, one of the most prominent planetary types in both sci-fi and reality, need to be more prevalent and useful.
Throwin' in my support, too.
SOASE needs more planet types... you wouldn't even have to change the tech trees. You could make new types just subsets of existing types. Ie: Rock would be a more habitable subset (and hence unlocked by) volcanic colonization, etc. Just more variety to look at, and extra little perks (and flaws!) inherent in the world themselves would add a lot to the game.
And triple to Gas-Giants! They should be made useful: Trade bonuses (via star base trade capability!), higher crystal extraction on orbiting extractors (many gas giants have crystals floating around in them, just look at Uranus and Neptune!), gravity issues that make it harder or more erratic to move around in the grav-well, the ability to build TWO star bases, maybe make gas-giants similar to Dead-Asteroids, so that you can claim them and build tactical structures, etc, etc, etc!
While we're at it, let's not forget about debris fields and plasma storms and the like, either. Honestly, I'd like to see individual planets worth more, but have less of them - while adding a lot more of the various fields and what not with interesting aspects to them - they'd make for great battlefields and ambush sites and what have you. Having 90,000 planet(oid)s around a single star is a bit insane. More stars, less but more valuable planets, more random fields and the like!