Sure, just as you can now with an iPhone that's been activated already.
For almost a decade I've bought CDMA smartphones with bad ESNs for cheap on eBay, and used them as the same kind of device that eventually Apple sold as the iPod touch. (And for development.)
Especially after 2005, when smartphones started getting WiFi. I kept some around just for use with my Slingbox and Slingplayer on WinMo. It was quite cool to have little handheld TVs available in the bathrooms or for watching on the porch or late at night in bedIf my wife wanted to watch one show on the big TV, I'd use a WiFi phone with an earplug to snuggle beside her and watch a different channel.
In fact, I keep a couple of bad ESN phones charged up for when the grandkids visit. They love playing with them, and I'm not afraid of them being broken.
Heck, I'm looking forward to cheap bidding on some of the first bunch of CDMA iPhones that people default payment on. Of course, if someone figures out how to flash them on Cricket or something, the price stays high.
Very smart! I like how you think.