So. As you have asked input, here you are.
* For the events: I would believe that Homeworlds cannot/are seldom targeted by High or Catastrophic events according to numerous tests. However, the Homeworlds are protected, NOT the system in which they are. It means they can be destroyed because of a Star Destruction, as a star is targeted by this event instead of a planet. Of course, this hypothesis will be wrong if anyone here has saw a player homeworld destroyed by the Planet - Destroyed event.
As for the actual tests, is there a way to log all what happens in a given game without having to actually play? PTF spoke of logs, but I am not sure if they can do that and how you can activate them. I will run a few tests, hoping there will be no weirdness to alter the results.
* For the reproduction rates: (I haven't delved yet in the other changes in PvK Balance Mod) The cost to increase Reproduction in AIC 3.2 is 1000 points for 10%, while the basic rate was around 10%. So it means a +100% increase for 1100 points, whereas the best other facility requires 1500 points for a +50% increase (that is, +5% of reproduction rate). You can achieve such results by raising Reproduction to 106 (the Threshold) for 600 points, and then Environemental Resistance to 120 for 500 points. (I forgot to see that ER was cheaper than Reproduction after Threshold before in AIC)
On the other hand, with PvK Balance Mode, you can raise Reproduction to 110 and Environemental Resistance to 150 for the same 1100 points. (That is a +20% increase in the reproduction rates) Even if you increase the basic reproduction rates by 4% (that is, a basic rate of 15%), an increase of 20% means an improvement by more than two times. (+133%) On a world with 400 million inhabitants, a reproduction rate of 35% means an increase of 14 millions each year, which is better than the Replicant Centers (10 millions a year). Therefore, the Replicant Centers would only be useful on worlds with few settlers (below 300 millions) or in conjunction with an improved Reproduction if you can spare the points.
Finally, on a Homeworld inhabited by 2,000 million settlers, +35% reproduction rate means 70 million additionaly inhabitants each year, compared to 30 millions for +15%. That is quite an asset if you have many colonies.
So, perhaps you could consider improving the efficiency of Replicant Centers or decrease the researches needed to be able to build them? (You need level 4 in Organinc Engineering and Organinc Manipulation for now) Maybe a second level for this facility, "creating" 2 million workers each turn, could be made? (Especially if you increase the basic reproduction rates)
And as for the reproduction/environemental resistance at the Empire creation, I would support an increase to both Reproduction and Environemental Resistance characteristics, so that the cost needed to have a +10% bonus to reproduction rate should be around 1500 points. (It would also depend on other factors) But this is an approximative value as deciding of a cost to increase/decrease a characteristic is quite a hard job.
Obviously, all my post was only suggestions and my own opinion, so feel free to do what you wish with it.