I like this idea. Here are a couple of suggestions from me:
1. Instead of a free gene, you get two free vermillion from that building if the pet that finds it is fully researched. I chose two because you can already find single vermillion units on the islands. This way, finding the building is still a bonus over regular exploring.
OR:
2. You get 1 vermillion and 100 silver, the amount normally used to research 1 gene. Still a free gene research, but you get to choose which pet to use it on. Same result, different execution.
I'm ok with different rewards, but I don't like the mutation idea. I have pets that I don't want to mutate, and I think mutagen is too high a reward cost-wise.