Structurally, the cloud version was you logging into your iMessage account on a friend's computer. How could Apple possibly prevent that?
I think it actually makes a pretty strong case for Apple opening up a better interface that lets people achieve the same outcome they clearly desire so much, they'd even compromise their own security to achieve it.
Apple had plenty of ways to detect a datacenter full of Mac minis logging into iMessage accounts from all over the world, multiple on each machine, with custom software automating message sending, which I believe is even open source so Apple could look at it.
I think it actually makes a pretty strong case for Apple opening up a better interface that lets people achieve the same outcome they clearly desire so much, they'd even compromise their own security to achieve it.