Advanced Population Control

I found the existing ways to control populations (in particular the options to remove a specific population unit) quite lacking. Particular these cases vex me:

1. wanting to get rid of a conquered species, to make room for primary populations
2. Growing a Species population for the express purpose of genesplicing them into your Original as genehunter or getting the Collection bonus.
3. Generally having a "Xeno Preserve" for a specific, highly specialised species (like Eydyr).

I had some thoughts on improoving that situation, hopefully without too much Development work. Some of it might even be possible with game modding as is.

1. Original/Xeno (Non-Original)/Spliced Xeno/Unspliced Xeno:

At the core a way to differentiate between those 4 states would be desireable. At the simplest level, this could be a preference level for opeartions like Chain Gang, Genetics Alteration Lab, Feeding Pits. At the more complicated end, those would be additional options that only appear if valid:

Original Population would be your Original Population. This is in most cases your prefered population. It is primarily there if you want to grow a non-Original Population type
Xenos would be the only other option for non-genehunter Empires. Some Affinity specific options already pick these exclusively. But it would be nice to have those as prefered/excluded for other pop murder options. Naturally Xenoes would be prefered removal targets, if species Purity Law is engaged.
Spliced Xeno are for Genehunters only. Those are pops whose DNA you already Spliced into your Original species. They are effectively worthless, except for maybe filling out a System that is not 100% grown. This level primarily exists to seperate them from the Unspliced ones, wich I you may not want to accidentally process.
Unspliced Xeno is a special Genehunter case. Sometimes you want to grow a population for the express purpose of splicing it into your Original species DNA. You do not want to accidentally put them into chaingangs or Genetic Alteration Labs.

2. Murder pops:
This option just plain out kills a specified pop. No pretense about needing Manpower, Eating Slaves or the like. Just plain: 1 Turn, one pop unit less.
The techlevel for this should be pretty low. Naturally the option should filter the strongest between the 4 above cases. Possible downside: -X happiness to Original/non-Original population pops as apropirate for a few turns (you either purge all and quickly, or very slowly).

3. Xeno preserve:
Sometimes there are simply planets where you just do not want your Original Species to grow. Maybe the Xenos have a unique trait that makes them exceptionally suited to filling that System (some species in a 4 Gas Giant System). Maybe this is a case of growing a population for Genesplicing/to get a collection bonus. I see these ways to do this:

1. Make settling your Original Species in a System a explicit thing. Something like a 1 Turn Project that spawns one unit of the original population. Until that happens, your primary species simply can not grow in that System. This is mostly for conquests and pairs nicely with the "Murder Original Pop" option.
2. A special building. "Local Governance", "Xeno Preserve" or something. It blocks original pops from growing there or automatically migrating there (you can still send them there). Non-original pops might get a slight boost to happiness or something. Maybe it even acts like a earlygame "Autonomous Administration" and increases the System Cap with the growth downside.