[Pumic]

Will a blacklisted IMEI basically 'brick' the iPhone, meaning that it can't even be powered on to connect to WiFi or play games?

Generally speaking, the IMEI number Is added to a pool of blacklisted numbers and when you attempt to connect the phone with a given carrier, they will see that It's blacklisted and decline It.

After doing a few Google searches, it seems that you can change your IMEI through some methods after jailbreaking the device. This should allow you to connect the phone to a carrier.