Different prefered planet type by faction

i'd like to suggest that all factions prefer their own planet type. 

currently all factions seem to see terran/atoll planets as the best (no happiness penalty).

would be nice if the unfallen have the best happiness on forrest, if the sophons would like an arctic or snow planet.

this would also mean that terraforming should then for each faction targed their best suited planet and not only

go in the terran/atoll direction.