After several games played I found something that is quite annoying. More planet types, the less value in upgrading their population by research.. The increase is so small.. In non-DLC they are somewhat fine, because they are actually something if you own 2-3 or more of volcanics. or ice, or desert, but now they are very small, you are not likely to get more than 1 of each type in a edium sized map, and on random medium, random medium large it is big luck if you find more than 1 of the planet type your race can research extra population for...
Terran increase is good for all races, oceanic is good for TEC, the problem is with the other ones providing extra population..
So I think a minor increase in the percentages of the Ice, Volcanic and Desert population research would be nice, the way they are now, they are not much of a help for their high cost (except Advent, but what is the chance Advent will find a planet they cab research more population for?? very small, TEC and Vasari can research for 3 types while they can do only for 3, and terran planets are extremely rare, like desert ones).
Maybe for Ice 20-40%, for desert 10-20-30-40%, for Volcanic 25-50-75-100%, and maybe the new planet type increases could be higher than the current ones (though ocean is good for TEC), the chance to
1. find the planet type that your race can research additional population and
2. find more of them in a single game
is very small, and these researches don't really worth paying for them, and they could be a nice addition to the 3 races economy these won't give huge advantages for any race, but would justify their research cost more, even if you only find one of these (and most likely you won't get more than one of the right planet type in a medium sized game)