Sinner, yes. that is the same exact "method" that I tried using my Tilt. Like I stated and several others have stated, the particular 2 reps and one tech support person that I spoke to were more than happy to help and give me whatever plan I wanted, but... as long at that iPhone data plan was on there it WOULD NOT ADD THE MESSAGING PLAN. Now, as I said in my previous post, based on the history here on this forum, it appears that those of you that got it working and have kept it working are ALL on Family Plans UNLESS someone has hacked their iPhone IMEI to appear to be a different phone.
If you think about it, this makes perfect sense. They can try all they want to restrict what plans an iPhone can use as long as the iPhone is on the plan alone, BUT if you are on a family plan, most likely everyone in the Family is NOT going to have an iPhone, therefore, the plan has to be "open" and allow for Family Messaging which INCLUDES MMS.
My rep even told me that when he called in for me that they changed my IMEI to a phone that he had and was not using anymore, then they added the plan. Then they tried to put the iPhone back, and it kicked off the messaging plan.
Again, what I wonder is WHY they are making us go through all these hoops anyway. Why does it make a big difference whether or not an iPhone sends an MMS?? I have to think there is some ulterior motive. I saw a joke in another forum (or maybe this one) that with the next verson of the iPhone they are going to implement MMS and Jobs is going to stand on stage and act like it's the greatest thing ever invented.

Hell, if they do, I hope it's better than MMS!