Info 2 [Q] Possible Complete Unlock? Idea proposal

So, I've the Verizon 4g LTE edition of the galaxy s3 for a while now and a few months ago I really needed to unlock this phone for use on gsm networks such as AT&T and T-Mobile. At first I was okay with having Voice, Text, and Edge for data.
Later on, I switched to T-Mobile from AT&T and got an iPhone. Now I want to go back to my SCH-i535. There is only one issue: I broke the sim/sd card reader. Now this lead me to think about a possible way to allow for this phone to be able to be used on gsm networks:

Use the other carriers sim/sd reader.

So instead of replacing it with the standard i535 reader, I'll install T-Mobiles SGH T99 reader.

I want to bring this up to see if anyone already knows the outcome or if they can instantly prove my theory wrong before I buy these things.

All answers are appreciated. Thanks