How to make a custom keyboard shortcut WITH NO MODIFIER

This is a known “bug” which I don’t know if Apple will ever consider a bug.

The problem is that the list of browsers is generated “dynamically” each time you click on it (or at least the 1st time after Safari has been launched); the reasoning behind this is that different users will have a different set of browsers, so the list cannot be hardcoded. So given the above, the shortcut fails to work until the list has been “generated” by Safari. This occurs when you display the menu.

A possible solution would be to use Automator and create a service that opens the current safari page onto Chrome. But that’s beyond the scope of this answer.

TLDR version: There’s nothing you can do other than file a bug report at Apple if you want to stick with the same shortcut technique. Alternatives involve Automator.

This is not a perfect solution for your needs, but FruitMenu from Unsanity is the only utility I am aware of that will let you customize contextual menus. It costs US $15.00. It is not yet compatible with Lion. You could download a trial version and see if it will be helpful.

Any keyboard macro program such as Keyboard Maestro should be able to achieve what you need. You might briefly see a contextual menu pop up while it is running its macro, but I think you could live with that.