First i musst say the idea is not bad ....
An race give on here end in an conflict the remains to an friendly other race ... .... BUT .... ....
First ->
The other Race musst at last be an very good friend or at best an allie .....
I can only imagine this would happen automaticaly IF the 2 races allied .....
In all other ciscumstances - it should only happen if the receiving race (or the player) agrees ... NOT automaticaly
[sure - i can after an "forced happiness" make from all the new planets/stations and ships an new subordinate race - but why should i have so many extra work, and even then it is a bound between use two races where it was none before - with many consequences - so why should this happen - this make simply NO sense ...]
Second ->
After this have happen > Race A was destroyed and give me all remains .... it is still an planet with Race A here ... ?? ??? ????
so .... Race A was "not" destroyed .. or ..... maybe ..... ?
Third ->
Even if it was all nice .... i agree or we was allied .... why .... why i dont get the star maps from "Race A" .. and see "nothing" ... [except the actual sensor ranges from planets/stations/ships]
She transfer all to me ... planets ... ships ... citizens ... but not the explored starmap ??, ???? ??????
So you see ... the "basic" idea is not bad ..... but Horrible executed and get more problems and un-immersion than worth ...
This is sadly happen with more than this example and game mechanic in GC3 .. too often...
Regards
[oh - and sorry for errors in my english - it is not my primary language
]