I disagree. I think the rear touchpad was a fantastic idea that doesn't get enough credit. Here's the thing. Implementing secondary shoulder buttons and clickable sticks was always a tough task considering the form factor they were going for. So they came up with a solution. A touch pad on the back to give you those extra input options. Without the rear touch pad you simply have less input options, because I can assure you that Sony would not have included buttons there if the rear touch pad wasn't there.
They should have refined the design until they got clickable sticks working.
Functionality > form. Vita is permanently gimped as a RP device because it's impossible for it to fully mimic a Dualshock.