Suppose that an empire consists of baseline humans and two subspecies: "paragons" (+8 temperature range) and "Titanians" (+8 temperature range, -30 base temperature. ) Would I be able to use genetic modification centers to convert paragons to Titanians, and vice versa? (For that matter, could I convert the subspecies back to baseline humans if I wanted to?)
If so, I see no reason not to convert the entire population of every colony to paragons (except for residents of Titan, who I would convert to Titanians, of course); I could always convert them again later if I wanted to go out and planets that are too warm or high-gravity or whatever. If, on the other hand, the first round of genetic modification is completely indelible, I probably won't bother with it at all; I'll just use terraforming and infrastructure.
Thanks in advance.