Thank you for the feedback and ideas :).
The reason we can only incubate a few of the species is because the original author did not left any more CGs for birth, so if we want new birth scenes we have to pay for new CGs and animate them ourselves, like we now did in 1.45 to add the mosquito one.
The issue with this is that it costs money and a lot of time, so we have to choose which scenes to add and which to not add due to the limitations. There will be a few other incubations, but not many more unfortunately :/.