Also it would be good if the worlds actually had bonuses and penalties that were appropriate to the type of planet.

For example heavy gravity worlds would get a natural defence bonus because it's harder for foreign soldiers to mobilize, but might take a produciton hit because it would be harder to work.

Radioactive worlds might get a boost to production because the nuclear material could be used as a power source but take a morale hit because of radiation sickness.

Aquatic worlds could get a tourism bonus, while barren worlds had a tourism penalty, but have better sensor range because the sky is clearer.

I kind of like the inhospitable planets but hate a couple things about them. It always seems like the inhospitable planets are incredibly high PQ, 11-15+ planet quality is not uncommon. It's incredibly frustrating to start the game on a big map with your choice of a 5-10 PQ6-8 worlds in settling range and another half dozen PQ11-15+ worlds that some AI will move into and start yelling at me for influencing the glowing rock of influence tiles they setup next to my homeworld.

Logically these inhospitable worlds would be the low planet quality worlds.

I tend to concentrate my efforts on just one or two new environments, especially if there are quite a few worlds of that type in range. This gives the AI a disincentive to research that colonisation tech, since they'll find that by the time I'm done grabbing there's none of that type available. By researching a different tech they'll be able to settle near their homeworld, not mine.

I've found that on any given map, there will not always be an even split of habitability types. Sometimes you'll get a map with more Aquatic than Toxic.

I agree, just stick in the option for a slider.

You could create a mod - modify the tech tree to make it impossible to research toxic or whatever. And keep super-abilities switched off since one of them gives a race the ability to build on other wordls from the start. Or simply go back to Dread Lords without the add-on. Unless you like some of the other new features of course.

It would be easier to set the research cost to 0 (any tech with a 0 research cost i given to everyone free) but that only solves the problem if you want to get rid of them entirely.