His problem ATM is that he removed siriport, and the settings.app is removed since its part of the springboard.plist, which is unique to instance. By replacing it with one off the net, you get the basic springboard back but none of the specifics
Sounds like the easiest solution would be to just back up your iPhone in itunes and do a DFU restore and rejailbreak your iPhone and install siri again. Siriport for iOS 6 is still in Beta stages so I would not recommend using it. Just my opinion. Do what makes you happy!
If the OP wants siri on his iPhone it's his choice. You are true in saying it shouldn't be used in an iPhone that doesn't natively support Siri because the hardware is not built for it, but again its the OP's choice.
If you restored to factory settings (no jailbreak) you shouldn't have any issues. Sometimes there are a few issues but nothing that can't be solved with a simple restore. Unless its hardware related.
Nothing should be wrong with it now unless you get a hiccup during the restore process, which rarely happens. A missing settings.app isn't a big deal. I once fooled around with my old iPhone's root, and accidentally deleted my settings.app and my phone.app. Restored, fully functional until it got replaced with my 4S