I'm about six years in my test campaign for v2.00 and I've discovered 48 systems, which means I have already encountered several challenges in dealing with eccentric orbits.
As an example, I've found what would looks like an amazing planet. Great mineral resources and a diameter of only 3200 km, making it easy to terraform. However, it has an eccentricity of 0.61 and it orbits between 6m and 26m km from the M3-V primary. So far I have added 0.37 atm of atmosphere, including 0.06 atm of water vapour.
Alexandria-A II Survey ReportDuranium: 2,320,076 1.00
Neutronium: 21,670 0.50
Tritanium: 5,921 0.90
Boronide: 1,584,327 0.80
Mercassium: 8,861 0.90
Vendarite: 1,618,984 1.00
Uridium: 375,773 0.90
Corundium: 1,380,521 0.60
Gallicite: 1,446,752 0.70
The temperature ranges from -78C to 122C over a 23 day orbit, which has two effects. Firstly, the water is frozen, liquid and vapour at different points of the orbit, with a knock-on impact on albedo and water-related colony cost. Secondly, the dominant terrain changes multiple times per orbit.
Given the above, I am wondering whether to change hydrosphere type and dominant terrain to be fixed for the entire orbit unless the environment changes via without terraforming. If I do make them fixed, I also need to decide the parameters. For example, should the dominant terrain be possible across the whole temperature range, or based on the average temperature? If average, should that be based on a straight (min/max) / 2 or take into account that planets will spend more time at the min temp due to orbital speed.
Hydrosphere would have to be based on some sort of average because there is no single state that could exist across all possible temperatures. Or maybe I invent a fourth state for water, that can be applied in that case and has its own effect on colony cost and albedo.
Also, does the year make a difference. This planet has an orbital period of 23 days, but others could be years or decades.
Finally, leaving things as they are is also a reasonable option. In this case, colony cost would reach 2.00 at certain points in the orbit due to the water evaporating. I would have to bring the temperate range down, accepting a lower temp at the minimum to bring the max temp within the liquid water range. Terrain changing regularly only affects ground combat and surface-to-orbit. Invasions would have to be staged in the best 'season' for the attackers.
I'm laying all this out to spark discussion