I will disagree with you here. The purpose of good siloing, IMO, is to make sure the characters are roughly equal to each other by avoiding the large disparities that a freeform or point buy system would allow... yet feats are just a poorly disguised point system that crosses the boundaries that the siloing creates.
/snip.
Bold mine
I think, Imaro, this is where you differ from many here. THe purpose of good siloing isn't to make characters roughly equal to each other.
The purpose of good siloing is to make sure that characters are roughly equal to each other
within the parameters of a given game element.
In other words, all characters contribute to combat in roughly the same level, all characters contribute to out of combat to roughly the same level. Sure, fighters aren't as good skill wise as rogues, for example, but, that doesn't mean they are completely incompetent.
Complete incompetence was a 3e thing. In 4e, at the very least, you get half your level plus ability in any skill. Sure, the specialized guy will succeed far more often, that's true. But, that doesn't mean you will never succeed. Within the silo of skills, everyone can contribute, just as within the silo of combat, everyone can contribute. It's just that that contribution will be different.
At no point should you be completely inneffective in a well silo'd system.
If you are adding "Domain Governance" as a silo, EVERYONE gets it. It costs nothing for basic competence. To be a good Domain Governer, you spend feats to improve that, perhaps buy magic items, spend resources, whatever.
But, the guy that spends nothing still starts off with basic competence for free.
Now, if you choose not to use that, that's fine and no system will help you. If I choose not to participate in skill challenges, no amount of skill competence is going to change that. But, that's up to the player.
What you don't have is five people sitting at the table playing five different games, which is a problem that occurs with non-silo'd systems.