Evil scientists build? (Experimental Sentencing + Cosmogenesis?)

I'm looking to play a build where I behave like the stereotypical sci-fi aliens, abducting xenos and using them to advance science at any cost. I would like to maintain a single main species as citizens and ideally not use them for experimentation, leaving that to conquered/enslaved xenos.

For ethics I'm thinking xenophobic + fanatic materialist or materialist/authoritarian.

Experimental Sentencing seems like a perfect civic for this idea, and I'm set on doing Cosmogenesis and making use of the lathe. I have some questions on how to build this though, namely:

1. Is it better to start with experimental sentencing or transition into it midgame? How much does it conflict with/make obsolete the synaptic lathe?

2. Are there any particular ascension paths that would work well with this build?

3. What other civics or origins would work well here?

Thanks!