Unless Tom has lessened on this point and I'm unaware, I do believe this is one of those 'frequently requested; frequently rejected; stop asking' requests and should probably be closed by a mod.
I believe it was, but that was determined long, long ago. And then, it was fine. But with the duchy changes, and the whole lot of problems that are generated from it (I suspect more and more realm merger cases will arise as time progresses, not less), I think it's a natural and necessary evolution of the game. Recruitment in the capital only was fine when every city was its own duchy and it was practically impossible to merge realms in the vast majority of cases, because precisely breaking the rules was hard and obviously exploitive. Now breaking the rules is neither, so it's time to just make it so the rule no longer has a reason to exist.