Atoll/Ocean Temperature and Late-Game Terraforming

The way that terraforming works currently is that if you have a hot non-T0 planet, you can terraforming it up the ladder to either a hot, or a temperate planet. There are no options, however, to terraform a temperate planet into a hot one. Furthermore, two T0 planets (Atoll and Ocean) are only accessible if you keep terraforming down the hot/cold line, but the end result is that they're temperate instead of the temperatures of the lines the player dedicated themselves to. Why, if I stuck to hot planets from lava to jungle, would I terraform my jungle planet into an atoll? Or my boreal planet into an ocean? The advantage of hot planets is their higher industry, and cold planets their science, but this goes beyond their inherent stat bonuses. many industrial buildings provide bonuses dependant on the planet being hot. A late-game improvement in particular is only usable on planets that are either hot or sterile (AI labour). "Upgrading" from jungle to atoll would cost me 5 production per pop on this planet. Likewise, going from boreal to ocean would cost me the cold modifier, something I definitely wouldn't want to do if I'm playing the Sophons due to the many science bonuses from cold planets. When you factor in planet specializations, it becomes even more lopsided, as there are no specializations which benefit from temperate planets (as for that, I suggest influence specialization. unless I'm really hurting for influence, I'd sooner go with food specialization than that. Lore-wise it makes sense as well, as people tend to be more temperate in temperate weather). I, personally, would much rather have 2 hot and 2 cold planets than 4 temperate planets.

My proposal is to change the end-of-the-line planets at the top of the hot/cold chains to be hot/cold as well, to give the player any kind of incentive to pick it after sticking with their chains up to boreal/jungle. Furthermore, I suggest allowing steppes to terraform into tundra and savannah terraforming into mediterranian, allowing players with adequately low-tier planets (such as these two and toxic) to pick something other than temperate if they so wish. Considering steppes environments tend to be rather cold and savannahs rather hot to begin with, pushing these environments furhter to their potential extremes should not be too much of a stretch anyway.