Setting to turn off minor faction assimilation

Just realized that it could potentially be a fun setting to turn of minor faction assimilation in the pre game options. It could add a bit more political flavour for those that want it. because as it is now its far too easy to assimilate a faction and it takes out a bit of flavour in the galaxy. That could be done via a simple tickbox turning assimilation off. Would be my idea and suggestion for a quick and simple change.

 As for the trait its not that simple then as a tickbox, that would require development time to make a system. For example to reward the faction trait with the quest maybe instead of assimilating the faction via quest. Or declare war on them to steal slaves for pop and tech and acquire the faction trait that way. Maybe make it possible to the minor faction to give the trait to multiple factions and take it away again if relations turn sour. Or any other, more thought out way. Could even add some diplomatic options for minors like treaties and such. Or anything else. Either way that itself requires work then, and is not a quick and simple change.