A "security" boot parameter is a bad idea, because it's behavior would be subject to change from version to version. This is not desirable for a boot parameter.
Instead, a wiki entry containing helpful tips and scripts to "harden" Tiny Core is the best approach.
If I can voice my opinion from end-user perspective, secure Tinycore, which means with proper user entitlements and not automatic inheriting root privileges through sudo is very important and should be default, rather than special boot option. It is OK to automatically log in as user, but system changes, including installation of extensions should require root privileges, therefore root password at least.
The way it is implemented now it is certainly far better than running as root. For this reason alone systems running as root such as Puppy are not acceptable for any serious use, but only for emergency recovery tasks.
One small change I would ask on the way is to require root password on sudo (I think SliTaz does this, not speaking of fat ones, like Ubuntu).
However the ultimate goal I see is to make it eventually multi-user by default. Even for a single user, a standard security is better than half-way security. Although TC is small today and meant for a single user, it is designed with modular architecture after all. This means one should be able to compose a system to his requirements from components on the base of TC core, including fully functional multi-user desktop systems. I would rather such core limitations not stand in the way of this possibility...
Just my two cents from user perspective...