What a lively discussion!
However the ultimate goal I see is to make it eventually multi-user by default.
Robert may choose weigh in, but I believe that is not his ultimate goal. As you work with TC, you realize that its purpose is to be flexible enough to enable everyone who uses it to reach their own individual goals. As useful as it may be to the average user, having firefox bundled with your distro can be an impediment if your goal is to create a router that fits on a 16MB flash disk. The fact that the noautologin feature can be added via extension without remastering is a testament to its flexibility. It enables one to achieve the "multi-user" goal even though it is designed for single-user operation. I expect it is possible to create extensions for NIS or LDAP to achieve even more.
I do not disagree with any of this. By my saying that TC should be architected as multi-user by default does not mean to enforce it regardless of purpose of specific implementation. This is a modular architecture we are talking about after all, and different implementations will have different needs. E.g. it would be pointless to enforce multi-user security for embedded appliance, where not needed. All I was saying was that multiuser capability should be available in the base architecture by default, so it would be available for implementations where required, without complicated modification. And it would not be used where not required. This is the beauty of TC architecture after all that by selecting components and features, system can be molded different ways to requirements, according to the intended purpose.
I see there is hardly any difference of opinion here, except I see a significant value in having such capability available in the architecture vs. having to seriously customize in order to accomplish this.
To emphasize, I completely agree that TC should be flexible to accommodate different purpose implementations. If I was understood differently, I did not mean to create such impression.