If you are switching to VZW just trade it in for a iPhone 6. If you want the 16GB it'll be free (which is the same thing as you selling it for $200, without the hassle.) Or if you what a higher capacity there is still $199 in trade in value for you!
This is always confusing to me. I've gotten more than one replacement iphone from the Apple Store, & while setting it up there is a screen to select your provider. All of them are listed (vzw sprint tmo etc)... Doesn't that suggest that at some point the phone can be reverted back to the same state & reassign a new carrier??
For Verizon they have to allow the meid number into their system unless that phone was originally meant for Verizon they will not allow that phone to be activated on their system.